Inspiron 531 new psu and graphic card

I know there are a few threads on this, but none seems to answer these specific questions, so here it goes..

currently i got dell inspiron 531
Amd x2 5600+
3gb of ram
geforce 8600 gt 256 mb
and the psu that came with the pc
(i didnt upgrade anything on this computer yet)
So i was wondering if So i was wondering if i could fit(and i have no idea wht psu i should be looking for..i think an ATX with 4 SATA and 1 pci-e connector?) http://www.futureshop.ca/catalog/proddetail.asp?sku_id=... in it..i'm basically looking for a 500w+ psu, but that can also fit in my case.
Also, i was wondering if the 8800gts(ive heard that it's a very good card) could fit in my 531 case
Thanks