GM latency issues in Windows?

Not sure if it’s just me or what, but ever since I switched from Windows 98SE back in the 90s, I haven’t been able to use GM for composing. I have a Win98 machine set up with SX1 and Cakewalk 9, and I get flawless performance with microsoft GS wavetable synth, and yes, i like to use microsoft GS wavetable. I know Windows 7 has a redone MIDI system in place but this was the same in XP and vista for me.

Is there something I’m missing here? All I want to do is be able to use that microsoft MIDI driver to compose and arrange (I do work in GM for mobile/social apps and games and such) without the ridiculous latency. I’ve had to resort to using Halion but that doesn’t translate evenly when exported to GM and it’s a hassle to use compared to just putting in a patch value into a simple midi CC and getting to work.

I’m running:
Cubase 6.5.3
Windows 7 x64 sp1
i7 2600k, 32gb ram
Delta 1010, Steinberg CI2, UR824

I’ve been trying any and all combinations of ASIO drivers and Direct X, no change in results. I know it’s most likely a Windows problem, but is there anything I can do to get decent latency out of it?