So it looks like the best combo for Virtual machines on my box:
- QEMU/KVM for all Linux guests
- PCem for Windows up to and including 98
- VMWare for Windows XP onwards
I can run all three with good performance and have 3D passthrough where needed. Virtualbox would have been in there if I could run it at the same time as KVM.
If I get 'Super Serious', having a GPU dedicated to a Windows Guest via KVM/QEMU is probably the way to go. That might involve a separate box.