Core.i7.920.6Gram1GGForce9400GT-VS-AMDPh2X4.920.4GramATI4850

The CyberPower has a much better Video Card for Gaming, also twice as much storage. The PII X4 920 might game better at stock speeds over the i7.

The iBuypower i7 is with out question the better choice for common applications and multi-tasking.
If this build had a better Video card there would be no question as to which is better for you.

With that being said my choice in your situation would be the iBuypower with a future Video card upgrade in the works.

You might also call each Company and see what kind of customer service they have.
Ask questions etc. If they are not there to help what good are they?

Sorry, Morning!

Sobered up now(ish)! B'oh!

having read the question properly, the i7 would be the best bet for video editing! The other PC is more rounded but completely over-priced if they cost the same.

Are you uncomfortable building your own system?

Best bet is to forget about that 3% Amex rebate (you're only talking about $27 here), and build your own. There's plenty of guides here on Tom's and elsewhere. Myself, I'd prefer the i7 but either an AMD 940 or i7 920 would be a good choice, esp. if you want to overclock or add a 2nd video card later.

For an i920 system, you can get one for $230 at Microcenter if there's one near you, Asus P6T mobo ($170) and 6GB of DDR3 memory (~$100). A decent 1TB HD is less than $100, and look for a good case + at least 650W PSU for ~$160 on Newegg. Newegg also has the Sapphire 4870 on sale this weekend for $190. Total cost so far is $950 and you have a much better machine, for about $77 more than your target systems, less mouse, keyboard & display.

Be aware however that if you do decide to oc, a better cooler than the stock one would be advisable.