some infos about the unpleaseant surprises that await you when running a 64bit AMD CPU on Windows:
http://www.pcworld.com/news/article/0,aid,112749,pg,6,00.asp

In short you have 2 choices:
- stick with 32bit Windows and have your Ferrari CPU unable to switch gears past the 3rd out of 6 available.
Wait 2004 Q1 (I doubt billy boy will meet the deadline) for a crippled 64bit version of Windows: basically you it will require most drivers to be ported to 64bit even trivial stuff like joystick drivers.
This means lots of compatibility issues which will convince most of the Windows people to stick to their 32bit Windows.

Fortunately the Lionstracs Mediastation runs on Linux which is fully 64bit capable since years (it runs on dozen of CPU types).
I'll let you know about benchmark numbers I get out of LinuxSampler on a AMD 64bit CPUs in TRUE 64bit mode.
with sample sizes that can be up to
2^64=
18446744073709551616 samples which at 96kHz amount to 6093150 YEARS of sample length ;-)

cheers,
Benno http://www.linuxsampler.org