I dont know about completely outperforming your current desktop, but it really depends what particular type of 295 youre going to purchase. Is it a 295 with 1gb memory? More information would help, I can tell you everything you need to know if you just provide a tad more info. If you purchased a gtx 480, im 90% sure it would outperform your current setup and the 295 by far.

Thanks,

-Acid