Optiplex 790 (large tower) and a 750ti?

[SkittishGaming]

I have a dell optiplex 790 for free from work. I wanted to upgrade to a gpu. I decided to have a 100 euro budget for the whole system (without OS, monitor) . I can get a 750ti for 85 and a crap hdd 320GB for 15. I was wondering if it would fit and would be powered adequtly?
Can you upgrade a psu for a btx form factor case? I can get a 660ti for 65euros.
Also largest form factor.

THX for help

 

[clutchc]

If this is your 790: http://www.garlandcomputers.com/wp-content/uploads/imported/Dell-OptiPlex-790-Mini-Tower-Intel-Pentium-29ghz-Dual-Core-8gb-1TB-DVD-RW-231195130475-4.jpg
...it should accept any std. ATX PSU available. It is not a BTX design.

Assuming you have the mini tower above, the 265W Dell PSU with its two +12V rails rated for 17A and 9A are sufficient for the GTX 750 Ti. I have one running in my 790 SFF on a PSU with just the 17A rail.