Background:

35 yo, married, 5 kids, wife stays at home
Secure job that provides EVERYTHING (house, medical, utilities)
Moderate income, but no opportunity for increasing salary or career advancement (and I don't really care)
Employer provided 10k/year into retirement account
Cash flow allows for additional ~10-15k/year being invested
Currently have ~$125k in various retirement accounts and another $125k in an investment account from a FIL life insurance payout

I feel that I'm sitting pretty compared to where I thought I would be 10 years ago in terms of retirement and my investment situation.  But I guess call me greedy.  I just got done reading "Rich Dad, Poor Dad", and feel I could/should be taking my investing to the next level, above the passive work, save, invest, repeat model.  That would basically mean diversifying my money producing assets beyond mutual funds.

I'm not the type of mover and shaker that is going invest the time and effort necessary to make millions in the next 10 years.  I enjoy my free time and time spent raising my kids and being with my wife.  What do you recommend to "up the ante" a little in my investing without getting into something that is going to consume my soul?  Real estate seems daunting and would consume most if not all of my liquid assets.  I've seen ETFs recommended, but have no idea what they are.

Or do you recommend I do nothing, accept my middle class status, and just relax in the knowledge that I will retire someday, just not anywhere in the near future.

Decide what you want out of life.

Sounds like a nice middle class life might be fulfilling to you. That's great.

I want to be wealthy and am working towards it. I want to sit at home and collect 40 or 50k a month one day. Something inside me won't let me stop. I have to achieve it. I've definitely sacrificed for that and it's not for everyone.

But on the other hand. The day I have enough mailbox money, i'm done. I want to enjoy my hobbies and family (hope to have one by then). No way in hell i'll work till i'm old like a lot of guys.

Rentals are about 75% of what i'm doing for income beyond my day job. If you have specific questions I can answer them for you.

There is no "next level" of investing without being an active participant.

Stocks, Bonds, and Funds thereof are the pinnacle of investing and letting other people do the work.  ETF's are like mutual funds except traded on the exchanges.  They are typically invested in the same types of assets that mutual funds are invested in so it's not they are a whole new world of investing or anything.  They have pros and cons compared to Mutual Funds but that is another topic entirely.

Real Estate is the next step up for a lot of people but it does require you to be an active participant to succeed.  

Beyond that you have investing in your own business but that's an even higher level involvement and risk.  A lot of people fail because they try to force something to happen where no good market exists.  People try to make their passion their business and usually fall flat because they are under capitalized and didn't do any market research.  You can't just throw you dream out there and expect it to succeed.  It has to be something that fills a market demand or is so good that it creates it's own demand.

Have you thought about playing with peer to peer lending?  It's a bit more hands-on and risky than the set-it-and-forget-it investing that you've been doing, but you can put as much or as little into it as you want, and it won't take as much time as starting your own business.

In the other thread, wasn't everybody averaging about the same as the market?

I believe yes, historical market avg. vs. historical trends of peer-to-peer lending are very similar. So IMHO, it's more of a diversification thing, risk difference, timing difference. You can put cash assets in a sort of "CD" like vehicle that carries a little more risk, but get a lot more reward; but not necessarily the same reward as the market. The major difference that I see is that barring major economical troubles, P2P lending seems a bit more of a "sure thing" as long as you are well diversified. Of course, if we have another down-turn the likes of 07/08 I would expect similar losses to those of the stock market... but one thing to consider is that the stock market seems to be a bit unpredictable and "wishy-washy" sometimes, where-as there would likely be a lag in the P2P lending. If the market goes south, you lose "liquid value" immediately, but in P2P lending you would still see decent returns for a bit until the trickle-down effect starts to hit people hard and they can't make the payments. It would give you a little more time to observe and react, and you don't HAVE to be active all the time to avoid big losses (like the market), if things look questionable you just stop buying, the loans you've already issued are locked in and you can't do a whole lot about those except hope the payments keep coming.

Disclaimer: this is all just speculation and jibber-jabbering, I really don't know what I'm talking about, that's just the way I see things and interpret things...

Also, the market is currently in an upswing, so while 6-10% doens't sound amazing, it would be during 2008! Diversification is a beautiful thing!

Invest in funds that pay dividends???

As fella stated were going for that mailbox money as well. Property here is fairly inexpensive with great rental prices.  We're hoping to jump into commercial within the year.

There is no next level without active participation and the less you participate the higher the risk.

That's for real estate, starting a business, investing in someone else's business, Private Equity, VC, etc.  However if you know what your doing and enjoy it, it's fun as fuck, except when you fuck up, but that's part of the game.

My first choice for active investing is real estate, second is vintage coins.

There's all sorts of non-stock things you can invest in, for me I like the idea that I'm not competing with 100 million other people trying to find valuable stock. Instead I'm competing against a dozen or so other people in my market looking for a deal on a potential investment. That way I can come up with my own valuation methods, strategies, and hopefully overtake people who don't do a good job.

Mailbox money is what you seek. Do you listen to podcasts?

I suggest Biggerpockets, Kevin Bupp, and Marco Santarelli. Their podcasts will open your eyes as to why people get into real estate, for the freedom.

I thought it was for the depreciation and write offs.

Now we talking!

This is what I'm trying to do.

I plan on holding my investments for a very long time, so to generate some income, I try to always buy something that pays pretty good dividends.

Best of both worlds, right?