With a 146 and decent memory, which you seem to have (getting) your goal of 2.8Ghz should be more than achievable, probably at 1.4 volts or so.

Once you got all your kit built and new install of windows sorted I'm sure the advice and suggestions will flood through to you.

If you want some reading have a look at this http://www.dfi-street.com/forum/showthread.php?t=20823 which tells you everything you need to know (and more) about your proccessor and how to OC. It can look a bit scary and in depth, but should give you a good sound knowledge from where to start.

Dave