HP Pavilion A6430F Desktop PC at Circuit City:
AMD Phenom 2.10 GHz processor
3 Gigs RAM
640 Gig Hard Drive
Video card: NVIDIA GeForce 6150 SE
HP Pavillion 5600 at Best Buy:
AMD Athlon(TM) 64 X2 2.8 GHz processor
3 Gigs RAM
500 Gig Hard Drive
Video Card: NVIDIA GeForce 6150 SE
OK - the 640 vs. 500 HD probably won't matter to you - you haven't mentioned photo or video editing in any of your posts. No winner.
The video cards are the same. No winner.
That leaves processor and memory - everything else is kind of fluff
Someone wiser than I will have to point out the difference between the Athlon 2.8 and the Phenom 2.1. The Phenom is newer but the Athlon might be more mature.
And although both systems have 3 Gigs of memory, the CC one uses 667MHz DDR2 SDRAM (PC2-5300) and the BB one uses PC2-5300 DDR2 SDRAM. Again, I don't know why (or if) one is better than the other.
If the processors are equal and the two types of RAM are the same, it looks like a complete tossup between the two. FWIW, I like Circuit City better only because I root for the underdog and Best Buy is eating their lunch.