Been reading this with interest as I use Realtracks (RT) a lot. BIAB RT works well on my big PC, but I have had to strip a few things out on the laptop to get it stable.

Main PC - AMD Phenom II X6 1055T @2.81Ghz, 8G RAM, 1.5TB hard drive - Geekbench 7660
Laptop - INtel Core i5-3210M @2.50Ghz, 8G RAM, 1TB hard drive - Geekbench 2856

I use Roland SD50 and have given up with ASIO drivers as they gave me grief and I don't need them. MME seems to be less hungry and more stable.

I have also removed Sampletank as I never use it, may remove Coyote (only used for render and I've stopped using that now) and on the laptop I turn off background stuff like wireless, dropbox etc. and that seems to make it more stable.

BIAB MIDI on the other had works on much smaller machines and I used to run it on a little Netbook with a Roland SC8820 with no problems.

As others have said, the more you can throw at it, the better!!!