I also vote for the DPMS rifles. IMO, they are the best bang for your buck ARs on the market. I only own one in .308, a LR308 - that came out of the box shooting a hair under one MOA, grouping around .90" @ 100yds. Extremely accurate rifle. Right now, I've added a Magpul stock (PSG-1/SASS style), an adjustable gas block, Badger Ordinance aluminum free float handguard, and 2 stage match trigger. Now, it prints .55" w/ 168gr. BH Match ammo. I bought mine new for right around 1K, and it's been flawless. Lower and upper are rock solid, no play, and so far, the 1044 rounds that have been through it have never caused a FTF or FTE.
I wanted an Armalite Super SASS or DPMS LRT-SASS, but didn't have $2000+ to shell out for one, so I bought this one, and am turning it into a SASS type marksman's rifle. I have shot the Armalite Super SASS quite a bit, one of my buddies owns one, and it's sweet, but now, I'm glad I chose to get the rifle I did and upgrade.
The Armalite AR-10T rifles are good choices also, but they are more plain M16/Ar-15 lookalikes with normal handguards w/ delta rings, A2 style stocks, and tall post front sights, which can easily get in the way of certain optics. The DPMS comes as a flat top and no sights, which makes it more versatile, since you can add on flip up sights or just stick with optics.
Either way, I think you'll be very satisfied with the big AR. It's what America's battle rifle SHOULD have been, IMHO.