For what it's worth, I was convinced I needed to get a totally new PC to upgrade from X1 to X2.
I decided to try it once on my 5-year old Dual-core. 6 gig, Windows Vista PC using a 10-year old, outdated EMU 1820 PCI-based audio interface. I installed the 64-bit version.
Viola! It actually started up, and has worked flawlessly (so far) in recording and playing back MIDI and audio tracks from external sound modules. It also called up a very effects-heavy project I had created in Sonar 8.5. The only time it's crashed (so far) is when I called up a really effects-loaded project that may have contained effects that I took off when I deleted 8 and 8.5 from my system.
So...crossing my fingers that it will continue to work well with my 'old clunker.'