along with the desktop I bought my self a GeForce gtx650.
the wattage from my psu is good enough at 460 watts but is the card compatable?
sorry if I sound new to thing just looking for advice.
Your XPS 8500 supports GTX 660!, Power supply is strong enough, but there could be hiccups.
So, I don't see anything serious to worry about in terms of hardware.
There is little thing for you to worry about - Service Tag registration, since you purchased your PC outside Dell, you would have to register your Service Tag to get support, I would advise you to get on the phone now, for about 30 days after date of purchase you suppose to have USA based phone support, and after 30 days, it automatically redirects to India!
I am sure you want to talk to native English person, trust me, so get on the phone and find out now about registering your XPS.
Once again, don't worry about parts. If you can return 650, do it and get 660, your processor deserves better video card!