Question about UPS

hello everyone

i need help here, since i can't find wattmeter tools anywhere near my city, so i don't know how much my PC taking power from outlet, i tried the watt simulator i find on a site, but i believe professional/expert in here could give me more detailed info/recommendation

i need UPS for my PC... here the detailed regarding my PC :
DELL XPS730
intel quad Q9550
Nvidia 9800GT
Asus Xonar D2X
4 WD HDD SATA (500+750+500+750)
2 DVD-combo drive (LG+Pioneer)
seems there 3 case fan
12colored Led

and what my PC equipment supplier option give me for the UPS is : APC BR1100CI-AS or APC BR1500i
also my supplier can make sure which one is better for me, so i hope people in here can help me

if possible i prefer to pic APC BR1100CI-AS since the price different is lots
APC BR1000i is $200 while APC BR1500i is $345

thanks alot before! ヽ(´ー`)ノ

oh i am using Dual monitor although its not necessary to plug both monitor to the UPS

so a 500Watts UPS should enough for my PC right?
what if i upgrade my graphic card to newer cards like GTX295 or set SLI for 2 9800GT, will the UPS still sufficient ?

ups... i also forgot to mention XPS730 PSU, it come with 1000Watt 80%guarantee...

thank you again ^^

thank you very much for the help WR2 (^O^)/