Herc, I highly recommend building one. You'll take away more pride knowing you built it the way you want. It's not hard at all. With a $1500 budget, that's enough to go any route you want.

To add to what Rook said, I think there's only 3 companies that actually manufacture the lowers. Then they're sent to RRA, BCM, Noveske, Spike, etc. and just get a roll stamp engraving.

The only thing that I actually bought 'complete' was the upper receiver. I bought most of my parts from Bravo Company. Main items that you don't want to skimp on quality is the type of barrel and bolt carrier group (BCG). Lower parts kit (LPK) is your choosing. I have G&R tactical LPK, in which he picks all the best quality parts from the main manufactures and puts them together in one complete kit (about $80). It works fine for me, but you can spend up to $300 on a 3 lb. Timney stage trigger.

I'll leave you with some literature:
http://forums.officer.com/forums/showthread.php?81462-So-you-want-to-buy-an-AR-15-huh