Is there a way to get the GoG version of Homm2 to play the expansion town soundtracks instead of the original ones? Thanks.

The music in the most updated version of HOMM 2 Gold on GoG.com is in .ogg format, so I think all you need to do is replace the correct "homm2_xx.ogg" from the Music subdirectory (01-41, which can be mapped to Tracks 02-42 on the original CD Track List where Track 1 is the Data Track) with files converted from the soundtrack pack (which has all the original and expansion music in .mp3 format).

Best regards,
Steven.