I use an A2000 with 16Mb fast RAM on a GVP 030. 3.9 is a real memory pig. I ended up going with 3.5 OS which seems to work quite well. I don't have a Toaster though.
I still use 50 pin SCSI hard drives, one 4Gb and one 2Gb - also a SCSI CD-ROM drive (internal).
The best thing you do is add as much 32 bit RAM as your machine will hold - no matter what OS you use...
