One option would be to send the CD-ROMs to someone that has SX2 and have them render WAV files for each audio track. The MIDI tracks (SMF) could be exported as well … without the necessity of having the original VSTi’s used in the projects … which can be reworked by you later.
You still might be able to recover a substantial number of tracks. Even if you don’t pursue restoring all the works … and it might be worthwhile for certain pieces.
Using another sequencer (even on a different platform) should not matter if the project tracks are in WAV and SMF format. If the exports are done with the same start/stop points (each track rendered from the start point and through to the end of audio/midi for that track, then everything should line up precisely in whatever DAW you use.
The biggest obstacle will be getting the rendered WAV files to you. The file-sizes will be large, perhaps too large for some folks to upload to the cloud where you could download them. Even do, rendering onto DVD and popping in the mail would get it done with little fuss-or-muss.
I wouldn’t give up on salvaging your projects this way. I bet there are quite a few folks hereabouts that would be willing to assist with one-or-more of your projects. You can count on me if you want to go down that path.
I encourage you to make an attempt to retrieve those projects. We’ll all help you. I have SX3 (not installed, but I’d be willing to reinstall it) and I’m going to assume they would open in C5 or C6 as well.