Dell Studio XPS8100 with Antec EA750 and GTX560 *Help me ASAP*

I can't really give an exact answer,
but you have to make assumptions and approximations, as you have your case you can measure the dimentions of the psu places, and as for the GPU I think it would fit in, but to be accurate there are dimentions of the graphics in asus website to be sure, but you have to check the heatsink and north bridge as my old Optilex360's heatsink blocked me from installing a dual-slot card, so it's all about u measuring dimentions.
if they fit, you would simply expect great performance.

Thank for your answer. But like I said I am on a trip and I can't really bring a desktop with me T . T
Any one know the size of XPS8100 and any one know if it will fit??

ALso I recently found a picture inside  
http://www.google.com.hk/imgres?q=XPS8100&um=1&hl=zh-TW...

from the picture I can assume the PSU mostly will fit, but i'm not entirely sure about ur GPU, it depends on the white thing below [is it a heat sink?] because dual-slots will take more space bellow, you don't have to worry about the length of the video card, the height might be ur problem as it was mine. under my predictions, I would say it would fit, but I'm not entirely sure to be honest.
my advice is, wait a bit to see if other members can help, if not you can sacrifice and if it fails; either sell the GPU or buy a new mobo.
I hope you won't need buying new mobo because I've been through this and it was frustrating.

well thank : D it's night time over here so I will wait while I sleep