I don't have any personal experience with either company but I have friends who have bought from Cyberpower, and boy, was the work shoddy. Fans weren't connected, temperature gauges were in sub-optimum positions, and the case had a few missing screws so I'd stay away from those. I took a quick look over on Amazon at Ibuypower's wares and I have to say, building your own is really the most cost-effective way. I know you don't feel confident doing the work, so I am not suggesting you do, but maybe you have a friend who would do it for you. I build my friends stuff.
If that's the case, I have a fairly decent build set up on an Amazon wishlsit. It's about $1,700 right now if I recall, but that includes an HD monitor, sound system, and gaming keyboard/mouse. In fact, if you cut it down to purely performance based parts, and get rid of my fancy soundcard I would use for recording, it would probably hover in the $1,300 range.
Edit: I forgot to add what Ibuypower looks decent. I apologize for the stupidly long Amazon link. http://www.amazon.com/iBuyPower-Gamer-Supreme-AM972SLC-Desktop/dp/tech-data/B006O5ZIN4/ref=de_a_smtd
There looks to be problems with it, reading the reviews, but the first reviewer provides remedies for them all. Edited, Aug 4th 2012 3:17pm by Internuncio