Dell xps 8700 GPU replacement

[Annoo_]

I have a dell xps 8700 and i wanted to upgrade my GT 635 to a GTX 660 and I have a few question:

1. Will my current psu support a GTX 660?

2. if so, it has two 6 pin connectors that are labeled p7 and p8. Which one should I use?

3. Is the GTX 660 compatible with the xps 8700? I read in a different post that the bios can be locked and will not allow you to change the gpu.

SPECS:
Intel i7 4770 @ 3.4GHz
8gb DDR3 ram
Nvidia GT 635
460 watt (so i think) psu
1tb HHD

 

[Dark Lord of Tech]

Should be able to easily run a 660.

 

[tulsatech]

I have a Dell XPS 8700 and it can run a Nvidia GTX 970 just fine. All I had to do was update the bios and I was good to go. Though upgrading the PSU would be a good idea too.