The STE is a nice machine, you got a hell of a deal too as they go for $100+ easy on the bay. The STE is the ST Enhanced model, that came out in 1989 to come to par with the Amiga! It has 4096 colors and stereo sound. It also has four 1MB SIMM slots for upto 4MB RAM. (First ST to have SIMM slots for easy RAM upgrading) I have a bunch of ST stuff so if you need software I can hook you up. Unlike the Amiga you can easily transfer the disk images to 720k disks on a PC, even in XP.
As far as monitor and cables, check ebay or B&C Computervisions or Best Electronics.
