Only way to get a decent pre-built gaming PC is through NCIX. iBuyPower rigs are marked up to hell and they have a pretty awful customer service reputation.

My tips are-

Don't waste your money on a rig that has more than 8GB of RAM, a PSU capable of more than 750 watts, or an i7. Get one with an i5 or an AMD FX 83xx and a nice graphics card if possible. You want one with a 7850, 7870, 660Ti, 670, 680, 7950, or 7970 (ranked from slowest to fastest).