I am trying to put together a low cost .308 build so far what i have is Complete lower A2 sotck and this 20" Upper is this about as cheap as it can get within the A2 stock and 20" upper specifications for a .308 AR?

Probably as cheap as you'll find for decent parts, but Blackthorne has a 20" complete kit for $499. All you need is lower and mags. I'd buy the DPMS over that though.

I haven't read about many issues with DPMS so i figured they would be good to go.

Me too-most of the issues I hear with DPMS guns are that they won't stand up to a tough carbine course-for the average shooter they should be fine. I'm convinced that most of the "DPMS is crap" that I read is from snobbery. it's not a Colt or Armalite after all.
I want a DPMS .308 myself, but just can't come up with the money and I'm not selling my 1942 Garand to get it.
There was one shooter on the IA Hometown forum last winter who got a nice fat doe with a DPMS .308, the rifle worked just fine for that.

ETA-keep in mind that mentioning the Blackthorne kit was not a recommendation, just a comment that if you REALLY want to do so, you can get a rifle cheaper than the DPMS build.

Hunting is one of the reasons i want it and yeah i wouldn't get rid of that Garand either! I am thinking about selling one of my ARs to help get the rifle so hopefully i will only need to come up with a couple hundred more after that just have to find somewhere to sell it first

I cant imagine paying for the ammo to run a .308 through a carbine course i think my wife would kill me

For a couple hundred more you can get an Armalite AR10.Buds has them for $1233,well worth it.

If you're willing to use steel cased ammo it wouldn't be too bad. Last time I looked AIM had Tula for the same price as .223(something like $199/case). But I agree, my wife would kill me too if I bought 1000 rounds at once.

It's been three years now, but I had my local FFL order me a DPMS LR-308 TAC-20 (No longer offered) for $890 shipped. That was the dealer price back then and he only chagred a transfer fee and call in fee. I'm sure costs have increased but you can probably get a factory build a lot cheaper than what you are forking out. I'm completely happy with mine.

Define "low cost".  A brand new DPMS is barely a grand and used ones are common enough in the $900 range.

The upper and lower i posted links to should be right around $1200 that seems like a good deal for a .308 AR style rifle that should be just as accurate as any AR i have put together.

You could do a used M1a for under $1,000 . I did

Here is what I did for an Armalite/Eagle AR-10, the upper was a Christmas special (the LPK was too, from a few years ago):

Lower Reciever$172.06
Lower Parts Kit$42.16
Carbine Upper (Complete)$587.22
Flip up rear sight$80.00
GG&G Front Sight$60.00
Carbine Buffer Tube (mil Spec)$28.00
Slash Buffer & Spring$123.17

Total $1,092.61

ETA: I used a carbine stock body that I had laying around, but subsequently added a Magpul ACS