You'll have to spare some serious time finding both A600 and ACA630 accelerator since those stuff are badly wanted. A bog standard A500 is way more common to find and perhaps a better choice since newly developed ACA520 accelerator is coming up for Christmass ! Just to note it will also have same if not better mass storage solution right on board alongside a fair chunk of RAM, perhaps fitting your MIDI ideas. Otherwise, go for 1200 which has much shorter and cheaper upgrade path.
