Looking for a good sleeping bag.  
I have a military mummy bag.
It’s pretty good.  
Is the 5 stage military sleep system worth it.  Would it b a important?
Or is their a better bag or just stick with what I have?
Thanks

Wiggy’s

Better for what? Backpacking? Car camping? Emergency? What temp range?
Need more details.

Check out 'Big Agnes".

Car camping then emergency.
30 degrees and up

All my backpacking quilts and bags are higher end, hydrophobic down...simply for compression and weight.  

However, for value, performance, and quality?  Wiggy's.  

I haven't looked at surplus prices but the MSS (I have two sets) is a good system for car camping or home/vehicle emergency kits as well.

ROCK6

Nemo
Big agnes
Enlightened equipment
UQB
ZPACK

All dri down types, 650-900 goose down fill options.

Wiggys.

30 and up.

I like my marmot and snugpak.

30 and under I'll run my kelty down or add a down quilt to one of the above.

Also depends on if I'm hiking or glamping.

I’m a 20 degree bag guy. Check out campmor.com. REI had very good sales close last year on Black Friday (I believe).

Yes, the Military sleeping system is worth it in my humble opinion.

The price of the goretex bivy is worth the price alone.



https://www.wiggys.com/sleeping-bags/

They make one of the best if not the best sleeping bags.

Western Mountaineering

There are a lot of good brands it just depends on what you are doing and when.  

If you are backpacking in the wet then a synthetic bag is a must even though they are heavier and bit less compact.  

If you are backpacking and can keep it dry a down bag is lighter,  warmer and packs smaller.

I have four bags.  
1.  A -20 down bag for winter backpacking (a 30 year old North Face that is still great).  
2.  A 20 degree down bag for summer (A Marmot)
3.  A Slumberjack hybrid type synthetic bag that has a light inner bag and a heavy outer bag that you can use together or separately depending upon the weather and temperature.  I used that several years elk hunting in Colorado.  It was warm when combined but I generally hated it because I toss and turn a lot and the inner bag would twist inside the outer bag.
4.  A huge heavy Cabela's cotton duck synthetic rectangular bag that I bought before our last elk hunt several years ago.  Big, comfortable, not quite as warm but easier to wear some clothing inside the bag.

Regardless of the bag, if you will be on the ground a good pad is a must.  You will freeze your ass off even in a -20 bag on a fairly warm night unless you have some insulation under you.

If as you said you will be doing only car camping and it won't be too cold I would get a rectangular bag or one of the mummy bags that is advertised as being wider.  They are less restrictive and generally more comfortable.  For that usage spending huge money on a bag designed for backpacking isn't going to get you anything extra that you need.  You pay a lot for high loft down fill, fancy draft tubes and baffles.  Those are important in a lightweight but low temp bag but not so much in a car camping one.

We bought Wiggy's system bags when we moved to AK.  Nice bags, can adjust "warmth" as needed.

Edit: check out their deals on off colors.  I can't tell the color of the bag when I'm asleep and I like to keep as much of my $ as I can while still getting a great bag.

Edit2: they would not, and still don't, ship free to AK...something wrong about that!  We had the bags, etc., shipped to a friend's house in lower 48 and they the Wife brought them back on the plane after a trip to see the Grandkids.

Jerry opened his shop in GJ on a Sunday so I could get a couple of new bags for the wife and I to take to Utah on our honeymoon.  

I have at least 7 wiggys bags from 40 to -40, I've tested the -20 2 bag ftrss in -15 and was almost too warm.

They aren't light or pack down very small but they are tough and the insulation works when wet according to @opusxkc.

Good info thanks guys.  I found a good deal on a mss.  Can’t wait to try it.  
Hope I like it.  We ll see.