PSU Upgrade for a Small form factor X3900 Desktop?

[apoman]

I have my hands on a Low profile GTS450, but problem is that now I do not have enough power supply. My computer is a very small desktop, and I would like to find an upgrade for it that's suitable for both X3900 desktop and GTS450.

*Or maybe I should buy a new case? Is it hard building it?

 

[gropingmantis]

What size PSU does the case take (check here if unsure http://www.silverstonetek.com/techtalk/n10055_usa.php?area=)? The GTS450 requires one 6-pin PCI power connector right?