Cosmic Dreamer...

I'm glad if i can help any friend here as many folks here helped me in the past.

When you get 5080 the actual free memory is about 2MB from 8MB available onboard. So don't expect to do anything with that. That's the reason Roland says you need the simm addon to read and convert samples.

About you second question. Yes when you add 128 MB the onboard memory (RAM) isn't addressable any more so you have only 128 MB total ram memory.

Triton has 16 MB onboard and it's also ridiculous as Triton is a sampler (or something like that) and not a sample-playback synth like XV. It's a shame for both of them (Triton and 5080) not having full memory onboard while memory cost is so low today.

I have not try an external scsi zip yet so i could not say to you about possible issues. I've tried scsi CD (Plextor) and scsi data access chain (XV <-> computer scsi) using adaptec 29160 controller with no problems accessing AIFF,WAV and AKAI/S700 samples on CDs and host computer. You can only read and convert samples but not rewrite them.

Matrix control is just a modulation reroute between source controllers and destination parameters.
For example you can use a source value like key position, aftertouch, TVF envelope, TVA envelope, bender etc to drive as input parameter the pitch, cutoff, pan, lfos, tmt, tva, mfx1,2,3 etc.

It's not too different from the old Roland editing method. It is very creative by the way, if you spend some time on (small) LCD.

In general XV has nothing extraordinary or inovative. XV's plus is it's excellent sound, fx, and SRX samples.