Jim shared several choices for General MIDI sound creation; however, if you want to use soundfonts that you already have (I have the creative 2MB, 4MB, and 8MB that use to ship standard with Creative cards - and for some reason the defaulted to the 2MB soundfont, which never made sense). Anyway, here are some soundfont alternatives (not comprehensive).
Synthfont allows you to load a soundfont (GM or otherwise) and use it as a VST, or as a standalone to play through.
I believe version 1 is free and version 2 is not expensive ($17 for a lifetime license).
You can also load a soundfont into the Sforzando VST that now ships with BIAB/RealBand (it will convert the format) and select patches there as well. I can't remember if it comes with PowerTracks or not (but if so, it would have to be version 2017).
You can also load a Soundfont using the
Coolsoft Virtual MIDI Synth, which sets up a MIDI output port that acts like an external device and allows you to load soundfonts as your sound source. However, unlike a VSTi or DXi, you can't render directly to audio; you would need to record the output from your computer back into your computer (again, as you would do with an external synth).
I have a ton of soundfonts I've acquired over the years that I could probably share (I'll see about uploading them to DropBox sometime this week).