That Anvil Arms place looks expensive for the lowers.
Here's some other links for Lowers:
Lone Star Wholesale-AR15 parts & AR15 lowers,1911 parts
Aimpoint Scopes, DPMS AR-15 Rifles, Pro Ears hearing protection, AR-15 Parts - Al's Custom Gunsmithing
Firearms, ar15 parts, ar15 accessories, m16, ar15 kns
Gun Show cost for lowers is around what you see on the Lonestar site.
I have purchased a Rock River Arms Midlength upper. from PK firearms. It is OK as are all 16 inch upper, but its not as accurate as a 20 inch upper, and it is easier to shoot accurately with the 20 inch upper due to the sight radius.
Best Recommended Trigger for an AR15 is: Rock River Arms National Match 2 Stage Trigger - Standard $120.00 at PK Firearms. If you're carefule you can install it yourself. Pin Size is sometimes an issue. For the money you cannot beat it with anything.
OK. Now that's all the lower stuff, but if you want the best, most affordable upper you can get goto:
White Oak Armament POB 74 **Carlock, IL ** *****61725***** (309) 376-2288 ***********************
John Holliger is the guy all the Service Rifle Competitors goto for uppers and barrels.
Look under Complete uppers and get the one with the flash hider, if you want, or not if you don't care.
Getting one of his complete uppers would in my opinion be the smartest thing you could do as an AR15 owner.