I don't know if this helps, but you can get a versions of GSOS here for $20 or under:

http://store.syndicomm.com/index.php?main_page=product_info&cPath=3&products_id=48

If you're wanting to play around with it and see how it runs on the system you have now, order some disks. If you need more RAM, you'll know it then for sure.

BTW - That link is for 6.0.1 and the site recommends 2mb w/ hard drive. Otherwise bump down to system 5.