Now another alternative would be the New Frontier complete lower, 99 bucks shipped and a Del-Ton upper for 399. Total would be about 605 with a guess for shipping of 25 bucks, 60 for rear sight and 20 ffl fee.
I just put together a cheap AR, using the New Frontier Lower. Bought it at Joeboboutfitters.com for 99 shipped. Bought a DPMS flat top upper with M4 lightweight contoured barrel from Midway for 383.00 shipped (They went out of stock on this upper the day after I bought mine...) My FFL fee was 20 bucks (but I get to split that 3 way because this lower arrived today along with 2 Mosin Nagant 91/30 rifles and he only charged me the 20 bucks since it went on the same form).
First thing I did when I got home was half way check out the lower then slipped that upper on and put a 30 round mag loaded with tulammo in it and went and shot all 30 rounds. I had put a TruGlo red dot on it, with empy mag it weigh 6 lbs. I fired without flaw. About every other shot, I would pull the bolt back just enough to see the shell and ease it back forward and use the forward assist to finish loading (hey, it's something these sport owners can't do and I know it secretly drives them nuts!!!

). Mainly I did it because on the AR15 forum, I saw a thread from a dude that was say his forward assist wouldn't do that, both him and his buddies. Everyone else that replied said theres worked. Apparently he found out that maybe it was the ammo he was using (I'd have to check that thread again). Anyway, it worked with Tulammo.
It is the tighest fighting AR I've seen yet, talking about the mating between the upper and lower. I suspect this will loosen up with use. The pins that retain the upper are plastic as well. Only metal in it is the buffer tube assembly (and its commercial, not mil-spec), the TCG pins and springs. If the plastic upper retaining pins were to become worn, they would be replaced with regular steel pins. Everything in the lower can be replaced with anything from any other AR lower. I was told they used the commercial tube as opposed to the mil-spec to save money to be able to meet the price point they wanted. No big deal really, is looked and operates exactly like my mil-spec AR's.
The trigger feel is awesome! No grit, no creep what so ever. About normal weight in pull, but it just breaks, like snapping spaghetti. There was zero lube in the lower, I'm not sure what to use, but I fired it dry. Mags insert and release freely, no play when installed. Pretty impressive really, for a complete 99.00 lower. My biggest gripe about it is the molded in flat trigger guard. I don't know why they didn't put one more like what the sport has, would have been much better, IMO, and I wouldn't think it would have added anything to the cost.