My upgrade recommendation:
replace the barrel battery!
3.1 ROM (maybe DKB rom switcher for old games)
FatAgnus 8272 w/ 1MB chipram hack (depends on motherboard)
8373 SuperDenise IC
Amber Board or Microway Flickerfixer in video slot
GVP or Phase 5 68030+ accelerator w/16MB ram and SCSI-II controller
ZII graphics card (PicassoII+ or GVP Spectrum 28/24)
4GB scsi-2 harddrive
4x scsi internal cdrom (R/RW drive)
Fast serial board or ZII ethernet (a2065, XSurf, Ariadne)
ethernet hub connection or 56K modem for dialup
ZII memory board w/ 4MB (just to boost 16-bit system ram).
17" Sony Trinitron monitor
