With 45GB of data, almost any CPU will do. What will matter is that you pump up the RAM and the hard disk speeds.

Your 3.6 GHz HT P4 w/256MB RAM could be trounced by my P3 w/ 1GB RAM if you had a the stock 4200 RPM slow drive and my P3 had the fastest 72000 RPM drive I could find.

Think about it.

bob