08-01-2013 10:10 AM
There is a thread regarding a forum member who succesfully installed the HD7750 in his dc7800 sff with the same 240W P/S.
That card would outperform the HD 6450.
Here is the link to that thread and you can direct any questions you may have to him by posting there or by sending that forum member a private message asking how the card is working.
While the title of the thread pertains to memory, we began to discuss video cards.
I hope that helps.