I just noticed this, should this work well with OctaMED, I'd start to consider buying one of these.
[youtube]M6nnBp4Z0YE[/youtube]
I cant see any reason why Octamed would not work with the unit , although i cant comment on the Midi aspect im not sure if the add-on board is Atari specific or just a serial one like the amiga had.
What do you need Octamed for though ? There is always "Renoise" which has the advantage of having very similar keymappings to Octamed. Renoise is where Octamed should have ended up IMHO.
http://www.renoise.com/