You could also render the mods to AIFF or WAV using OctaMED SoundStudio or DigiBooster (not tried the latter for this but given it uses AHI, I don't see a problem using filesave.audio).
Once you have your PCM data you can convert that to MP3.
If you are a bit of an audiophile, read on...
I've done this with SoundStudio before. To get the best results, you might want to play with some of the samples (in particular increasing their sample rate, conversion to 16-bit, tidying etc) so that you can use mix mode at 44.1kHz with smoothing etc. Low sample rate sounds get very filtered at 44kHz with smoothing and can end up very muffled. Good for some samples, but way bad for anything supposed to sound bright - resample all those to at least double the rate (then transpose their instrument properties down an octave).
If you are really fussy, you can convert *all* the samples to stero too, then basically set the balance of each one (set the channel pan to centre) - great for drumkit sounds. Also you can make stereo chorus / delay effects with others this way, all of which eliminates that basic "4 channel extreme stereo" sound.
The end result can sound really nice if you take your time to prepare the mod file slightly (as described above).