thanks so do you think that my 600watts psu is good enough ?
you already own the PSU and it runs your ATI 5850 fine which would be the major power draw in either configuration (current or your upgrade) so you should be fine. Switching from the e7300 to the i7 will not be a major power increase (20-25w). you do know you will need a new motherboard (and probably RAM if its DDR2) ?
P.S. if the PSU is from the extreme series or one of those wacky lines and is getting up there in age (three or more years) then I would start saving for a replacement (preferably from one the brands mentioned above). If it's the silent pro 600w, you are fine as the PSU is solid.