dON'T RULE OUT THE va7!(damn caps lock!)
The polyphony is MUCH better than the PSR9000 and that should be important if you're composing large scores. The sounds are among the very best and the on board speakers sound wonderful. THere is a built in zip drive, so no need for a hard drive, and zip disks are plentiful and cheap. It has a terrific sampler called variphrase that takes sampling to the next level - it also has the new GM2 standard. The direct from disk playback is as good as any and WAY better than the 9000, because you can search for a new file while one is playing. The "gazzinta's & gazzoutta's" are more plentiful on the Yamaha, but if you are using it at home, you may already have some of the mic processing gear you need. Before you buy one - these are the top dogs at the moment:
VA7, PSR9000, Kn6000, X1, PA80 (soon!)and maybe even the MZ2000 (havent'd sen it yet)
Check them ALL out first - don't go on our recommendations alone - we are all very biased. (except for me - I am ALL KNOWing)
...To be honest - all I know for sure is that we all like different things about all of the top brands - it's a really tough choice if you plan to keep it a while. The technology changes at a speed that will give you whiplash. The best advice I can give you is this: Play them all, then buy whatever your budget will allow.......then STOP reading all these posts! It'll make you nuts!
Learn your instrument inside & out and be creative and productive. We all have a little too much time and advice on our hands and we (as a group)seem to go through keyboards like we change socks! THere is plenty of help here if you need us, but make a wise choice first - use your EARS, then read the manual and see if the features will suit you. There is a world of crap floating around out there mixed in with the good stuff. Be careful before you buy anything, because none of them hold their value too long. Hope I didn't discourage you - I love this stuff, but I can afford to change alot because it is my full time income, and I need the best toys all the time.(spoiled!)
From reading your post - I predict that you will like the Korg patterns the best with the VA7 second. Korg has an edge in the "pop" sounding patterns. Yamaha has great meat & potatoes rhythms, X1 has terrific Latins, and everyone seems to like the Technics for Swing/Big Band - although they all do pretty good swing. Over the years I feel that the Korg has the "hippest" Bass parts of all of them - even dating back to the earlier "i" series. Check it out for your self - the new PA80 should be in the states by the Winter NAMM show on Jan18th. I'd definatly wait to see if it fits YOUR bill. (I'm getting one no matter what)