Long story short:
Maxed 403b.
Maxed ROTH.
$2500/yr in 529.

Loans
Car at 1.9%
Home 3.65%
Solar 3.99%

I have about $1,000 a month in spare cash we are seeing stack up in our account I can start moving around. Do I pay off loans, add more to the 529, invest in an investment account, or hookers and blow (aka NODS, expand garage, etc)? I can see a positive to everything. Already have over $40k for retirement plus match, so paying loans quicker may help. 529 means another tax deduction, but my kids will probably get an academic scholarship. Enjoy the money I make and do some extravagant stuff, but I already buy whatever smaller things I want.

Unless you can safely make more after taxes investing than your loan costs are, pay off most expensive loan

Right now, I'd ensure I have a healthy cash position for an emergency fund to cover income loss (expenses) for a bad scenario (6 months to a year), then shove the rest into a taxable account and dollar cost average while the market is low (or even trending lower).

Personally I'd be tempted to make purchases in ETF's around every 30 days (or on exceptionally low market reaction days) and split that between VTI and VOO, so I could tax loss harvest along the way if the market trends lower, to avoid wash sales.  Or, if that sounds like a pain to manage, then just buy VTI on a schedule.

We are doing that already. We stopped the last 3 major projects around the house to cover expenses.

Get rid of the car note. It may only be 1.9% but it is a depreciating asset. Once the car is paid off then use that extra cash for more investments. Basically, if your car note was $500 then contribute that $500 to a brokerage/IRA while still using the $1k cash you spoke about on your remaining debts. Seems like you are financially in a good position and make a decent income. Keep up the good work!

Why does 1.9 on an asset that is static any better then 4% on another static asset?

If no one in your family has a chronic health problem where you are constantly seeking medical care, then the next time open enrollment comes around at work, select the high deductible/catastrophic health plan with HSA, then throw the most you can legally into the HSA.  HSA contributions are exempt from fed, state, and FICA taxes, the money grows tax-free, you can withdraw from it for any medically-related reason before retirement age (which is a big deal in your 50's), plus you can use HSA funds to pay COBRA premiums in case you lose your job.

Just the way I would approach it. I am making the assumption that the car is your lowest dollar value debt which would make it the quickest to payoff and reallocate the funds to for other items (debt snowball - pay off lowest value first regardless of interest rate). This might not be the case for you.

Some people believe that it isn't worth it to pay off low interest rate loans faster because they could invest that money elsewhere that returns a higher interest rate. I understand that thought but I like having the extra security of owning items so it is easier to weather the hard times in life. This is all about risk tolerance and is completely up to each individual. Which ever path you choose it appears you'll be fine.

Couple of items to also consider if you haven't already:

-Store your emergency fund in a high yield account. The wife and I use Capital One and earn 1.5% which is significantly higher than our local bank account. We use this 1.5% earnings in our brokerage account

-HSA like another member has already mentioned. Great tool if you qualify for it

I don't qualify for an HSA. Works insurance plan isn't great but far from horrible and affordable compared to what some people pay.

My car and solar loan are basically the same amount. Getting the general consensus that we should start paying loans at this point.

I'd look at it like this.

Your solar loan is 4% interest.  Can you make more than 4% in the market?  That depends on your timeline.  If we are talking 10 years, then historically the market has always provided more than that except a few 10 year periods, and those were specific periods that included a start time just before a significant drop in the market.  Given the latest market drop, this might be a great time to invest.  But since the market can still drop more, you have to have a long enough timeline to make that pay off.

However, if the solar loan has a 5 year term... and we are comparing that timeline, I'd be inclined to pay off the solar loan and earn the guaranteed 4%, since you are maxing 403b and Roth in the market (that's an assumption).

To me, your decision is all about your age/time where you might need the funds.