The best solution if you want General MIDI without any external synthesizers, in my opinion, is a PC MIDI, MPU-401, or anything with a wavetable header, and a Dreamblaster X2GS. It sounds very similar to the SC-55, is GS compatible, and will be self-contained within your computer. There are lots of PCI cards which also have wavetable headers, so you can easily supplement almost any build for this.
If you have any Live!, Audigy, or Audigy 2, there is a really good SC-55 soundfont. But it will only work from within Windows. It can also be used by DOS games for General MIDI if you install the legacy DOS device driver, but the game has to be able to run from within Windows, and not all of them can.
There is also a SCC-1 soundfont which would fit within the memory of an AWE32/64, but it's not as good as the SC-55 one. The reason this one can't be used is because it's about 48MB, and the AWE32/64 is limited to 28MB, I think.