Was 2.0.38 even 64 bit? I think that 2.2 or something was the first 64 bit version???? I could be wrong.
The other parameter that can be changed is how much of the samples get loaded into RAM so you can balance the RAM usage and HD through put.
Bottom line though, you got it working and you are happy.
Jim
PS - I use a ton of sample instruments in my work and have to tweak the engine of the sample players, settings in SONAR to balance the load so I don't run into any issues myself.