for me it's the excellent and low cost BPPC 060+SCSI with a GREX solution that bring me the best of what an Amiga can give, with very high compatibity from old apps and old games Kick/WB 1.3 up to MorphOS, and may be OS4 if there is a trick to use the Voodoo 3 or the Permedia 2 that I have on it :-D
