To speed up rebel assault use a Sound Blaster!!, and Sod the GUS!!
I recently bought a Sound Blaster 2.0 Value edition, and since then everything has worked like a dream! Rebel assault runs at top pace. I use the GUS for General Midi and The sound Blaster for Fx. Using this I can get Theme Park, Magic Carpet, Bioforge etc.. to run with sound, and I find that Xwing, and Tie Fighter run a lot faster..
You can get a SoundBlaster for about 40 quid, the same as cost as most games. So which is better? a New game, or full sound support on all your old games?