Yep, what organ said. You'll know everything is high quality because you built it . Large companies bulk buy "generic" parts to create a bigger profit margin.
My specs:
Motherboard: MSI K8T800 NEO-FSR
Processor: AMD 64 2800+ @ 1800-1937
Memory: 1024mb Corsair Valuselect
Harddrives: 80GB Western Digital 8mb cache & 120GB Western Digital 8mb cache
Video: BFG 6800GT OC 395/1090
Sound: Creative Soundblaster 24bit
Optical: Aopen 24x CD-Burner and Samsung 16x DVD+/- Burner
Misc: 3 red LED (2 rear, one top), 1 Tri-LED (side), 2 Blue LED (front grill), Zalman Copper 102mm Heatsink, 17in Viewsonic monitor, Logitech 5.1 z640 speakers, free newegg.com inkpen.
Guess how much all that was? 867 bucks over the course of 3-4 months. I used scraps from the old comp till I replaced the components (sound blaster gamer 5.1, aopen cd burner)
Now, tell me what your compaq, dell, or hp has inside it