AIM is a good company, not much of a selection but good prices/products. I havent done much research but I think the CMMG uppers are good:
http://www.aimsurplus.com/acatalog/U...ssemblies.html
If you want something really worthless you can even get an upper in 5.7x28mm
*edit: Just read that AIM is out of stock. Oh well, you could call and see if they have any coming in soon.
I'll be needing a new upper for my AR (jackass gunsmith fucked up the chamber and now spent cases get stuck). What I'd rather do though is grab a Sig 556.
Threaded Mode