Can someone help me? please I realy wana buy fast!

If not what wattage is comfortable?

Also the quality of the psu is more important than the printed wattage because a good 500w psu will give you more than a crappy 600w. For that video card you shouldn't have a problem though.

ok so its safe doing that setup? thanks

AMD's minimum requirement for the 6870 is 500w so you should be fine.

Buy fast, repent at leisure.

Price out the components, or equivalent at newegg first.

Diablotek looks like an absolutely terrible psu company. Jonnyguru rated a top unit as the pits.
Newegg sells the same psu for $28. No way that can be any good.
Look for Seasonic, Antec, XFX,Corsair, and PC P&C for quality units.

Post your budget, and what you need to do, and you will get plenty of builds form the members here.
I have no particular problem with the 2500K and other parts.

Its overclocled though how much more does that change it?

Is there any particular reason why you would want to build a $700 system with a $50 powersupply? I have had two PSU failures in the past (Thermaltake and then a more expensive Antec) and it really is a pain in the proverbial.

I'd personally look to purchase something branded that you can trust. You should also consider that if your PC is on much of the time, a branded PSU with a high efficiency rating may pay for itself in a couple of years compared to a cheaper inefficient PSU.

I just want to get that same exact setup but switch powersupply and my budget is maxed like $720 after rebates and stuff.

Zip, it is normal operation that you can simply do yourself. It adds value only to the uninformed.