I'm sure this has been done to death and through google-fu I thought I had it narrowed down until I hit "buy" and realized that I didn't.  Order cancelled, and here we go.

I have an Aero M5 lower on the way and I'm trying to figure out how I want the buffer assembly to go.  I'm of two frames of mind.  First I had a carbine length buffer tube and planned to use a 308 5.6 oz buffer and a Tubb's flatwire or a SpringCo Red.  Then I ran across the Kaw Valley Precision kit and changed my mind.  Does anyone have any experience with these guys? The KAW valley kit would wind up being $60 or so cheaper than if I pieced the whole thing together myself, but if it's no good there's no point.

For what it's worth I plan to pair it with the Aero M5 18" upper, which uses a rifle length gas system. It will be suppressed most of the time so depending on how hard it shoots I may switch out for an adjustable gas block.  I'd like to keep the carbine length but I'm not married to it.

Please for the help and thanks for the advice!

If you haven’t bought anything yet, I strongly recommend an A5 length buffer tube for a large frame.

They allow you to use normal AR-15 carbine buffers.

The Kaw is a great kit. I have one on a 16" mid-gas .358 Win. But as ziarifleman posted, the intermediate length RE would be a better choice for a suppressed 18". Armalite sells the kit for a decent price (DPMS compatible), but the service can be difficult. I'm not sure of the availability right now, even if shown as "in stock".
Armalite kit
ETA: Not all stocks will completely collapse to the castle nut with the intermediate RE, if that would bother you.

Standard AR15 carbine length tube and JP SCS

If you’re using an adjustable gas block, go with the standard weight

Non-adjustable gas, go with the H2 weight SCS

I am probably the only one, but I have had problems with the Tubbs Flat wire.  I ended up pitching it.

You can split the difference and go with an A5-length tube and the JP SCS, simply cut the included rifle spacer down to fit (or buy a pre-cut A5 spacer from JP).  That way if you ever want to expand your options outside of the SCS, you already have an A5 tube, and (usually) 7 adjustment slots as a bonus.

And I also recommend buying the dual-tungsten heavy (H2) JP SCS even if you're running an AGB, it's cheaper to buy replacement steel weights than it is to add tungsten to the lightweight SCS.  And while you're at it, get the three-spring pack version for even more tuning, and the RE plunger kit for convenience.