looks solid. You could step down to the 520W model of PSU, but as it is, it'll be a solid build, good or a couple years at least
+1 to ScrewySqrl on the rating (looks good overall) and the PSU recommendation as well. You can save a few $$$ going with the 520W Seasonic (great PSUs BTW) PSU vice your current 620W. I would further recommend that you use the x64 version of Windows 7. Good luck!