How is your physical interface connection right now?
(perhaps FPGA Replay may solve your memory requirement.. some 64 MB)
What do you mean, on my actual Amigas? My 1200's got 34Mb total, as does my 600, the other two have not been modified yet (need re-capped first), but the 34Mb has been serving me well as I like to use large talkie samples in the noiz I make.
Seeing as the Mig only has 4Mb, I will pretty much be using it as a controller only, though if I can figure out how to get the MIDI input working on my Akai XPM8, then I will not need to worry so much about the memory limitations.
As for the FPGA Replay, I fully intend to buy one of those also when the time comes.