A few other possibilities.
As pricey if not more so than the Protean Drums ROM ($250 to $300 on Ebay). Excellent and, IMO, still relevant for hand percussion and tuned percussion instruments. Programming the raw waves can yield some otherworldly percussion instruments.
Limited standard layout drum kits (IIRC maybe 10 or so presets) but all are pretty good and definitely fill in gaps in the MP-7 preset list.
The other instrument presets varied wildly in my eyes from lovely to crap but programming the raw waves can...blah, blah, blah...
For me, the ideal Command Station would start with the World and the Protean Drums
A couple other budget contenders:
A good one to have if you want a wide variety of acoustic drum kits for cheap. All useable stuff. I've never heard a PX-7 (and I'm dying to do so) so I can't say if it's a good substitute for one (probably not, I tend to trust Aeon's opinions) but for the current prices it's worth looking into ($150-is down to $100 and a bag of peanuts on Ebay). Not a bad jack of all trades ROM, either, and you may find a useable choir.
Sounds of the ZR-76:
I bought this for the Perfect Piano. I don't like the Perfect Piano (mind you, it's far more useable than any other acoustic piano that E-MU has on offer) but I like the drums. Some are better and some are worse than the Composer but none are bad. It too may serve as a good bread and butter soundsource. It probably has some choirs in it. I really like the bass guitars, synth basses and the organs. IIRC there are a few nice ensemble and solo strings (nice for a 10 year old ROM). These seem to go for about $150 US give or take. If I ever get my Command Station back (it's on loan to a friend) I may choose that over the Composer as the "all around" ROM.