Need Help Upgrading GPU and PSU

Ok after Extensive research I have come to a conclusion on the GPU and the PSU I want to buy.

GPU: EVGA GeForce GTX 680 2048MB GDDR5, DVI, DVI-D, HDMI, DisplayPort, 4-way SLI Ready Graphics Card Graphics Cards 02G-P4-2680-KR

PSU: Corsair Enthusiast Series TX 750 Watt ATX/EPS 80 PLUS Bronze 

The PC I have right now is the DELL INSPIRON 620 and no it's not the slim one

I need to know IF THE PSU AND THE GPU will fit and be compatible with the Motherboard and such.

This is the Exact PC I bought from dell > http://configure.us.dell.com/dellstore/config.aspx?oc=fddwrp12&model_id=inspiron-660&c=us&l=en&s=dhs&cs=19 

Please help me out? Thanks.