i use the Z board for gaming and typing and i've never had a problem. Spacing is similar to Logi boards and the feedback is similar to M$ - best of both worlds.
The Logi Mx 510 or 518 would be the mouse of choice for anyone and make sure you couple it with a decent mat.
a good PSU will remain a good PSU (at least in comparison) for at least a year and you'll only see a tenner knocked off the price within 9 months, if that. Try Tagan there always good.
Also about the 7800, it will blow your mind. I've had a 6600GT, a 6800 Ultra and now the 7800 GTX - amazing cards all of them, but the 7800 takes the biscuit, quiet, fast and a great overclocker
good luck with the build.