Now, I purchased a 720VA/450W UPS, and I'm gonna use it with my new CPU.
Here's the stats:
Intel Core i5 3.1Ghz 3450
Motherboard: Intel DH67BL LGA1155 socket
Graphics Card: Zogis GeForce GT-630 2Gb DDR3
RAM: 2 Ram sticks, each are 4GB, Kingston DDR3 1333
HDD: 1TB 7200 RPM SATA SeaGate
DvD Writer: It's a Samsung 22x SATA, but im planning to get a LG 22X +- SATA.
Not sure about the case though
If by "800W system" you mean 800W PSU, that depends on what the actual power draw of all components and PSU efficiency is since the PSU converts only as much power as its loads require. You could have a 1500W PSU drawing 120W to feed 100W to an idle system.
If you mean that the system is really drawing 800W then no.