Found out I'm getting a .450 Bushmaster upper for Christmas, problem is I sold my AR a couple years ago. Was thinking about ordering just a lower assembly, but looking at the sales I can get a DPMS Oracle for $500 or a Bushmaster QRC for $50 more and have a .223 upper. Any opinions on these basic rifles, or better options?

Bushmaster parts are more likely to be with in spec.

Primary Arms has complete Anderson rifles for $475. I'd take one of them over a DPMS or Bushmaster.

http://www.primaryarms.com/anderson-manufacturing-am15-with-fixed-front-sight-am15

this.
remember dpms is remington and if they do to dpms what they did to marlin i wouldn't touch them

And Marlin started in a better place.

Remington owns Bushmaster too. The pre-Remlin Bushmasters were great AR's. I've owned several over the years. Don't have any experience with the new ones.
The nephew has had a DPMS Sportical for 3 years and he has used and abused it with no problems at al. But that's just a sample of one, for whatever it's worth.

Nowadays, I'd probably go with the Ruger if I was buying a cheap AR.

There's so many AR makers anymore, most I've never heard of. Is Anderson a high quality maker? CDNN has an assembled lower by Invincible Arms for $150, probably the cheapest way to go but never heard of them either. I've heard good things about Ruger, but I haven't seen them on sale this fall. I'm concerned more on how the lower will match up with the .450 Bushmaster upper.

Yes this. I'd go with Primary Arms or Palmetto State Armory (either complete or separate upper/lower) every time before DPMS or Bushmaster. I've always been very happy with my Anderson receivers as well, both uppers and lowers.

Decided to build up an Anderson lower with the components I want rather than upgrade a basic carbine.............. Magpul fixed butt, Ergo grip, CMMG parts kit and Rise trigger.

If DPMS is Remington then so is Bushmaster. Actually it is the Freedom Group that owns them as well as Marlin, Barnes Bullets, and a slew of others.

Not a bad idea. I have several builds. Just know this, typically a build loses value much faster than a rifle made from a known manufacturer.