I saw a used Roland D10 61 key synth
in a keyboard store for 200 dollers +
2 dollers tax is this a good price?
It sounded good and has an expansion slot
but I don`t know much about it (polyphony and such) would it make a good addition
to my Alesis QS6.1?

It wouldn't be fair to tell you that the D-10 isn't a great little synth. It does have it's place in the industry. However, I don't think that youre gonna find any sounds in the little bugger that you don't have in your QS-6. (That being a board I've never used) but have heard and read alot about. The D-10, however I have some experience with.
It's an FM engine that can't recreate a good piano sound to save its soul ,as with my D-50 but it can make heavy duty metalic sounds(hammer on anvil and such). They are great for orch. parts Pads,Strings,etc. Stuff you already have. On the other hand, if you used it in your studio, or living room as a sound mod. hooked in conjunctin with your other board to develope layered sounds (more polophony) for the price, it might fit you fine. It all depends on what you're doing with. If you gig, and only have the one board, it's always great to have two, fast switches between piano, organ, sax and so on.
All in all, the D-10 is NOT a lead machine, but will fill in your mix nicely. If you could talk them down another 50 bucks, I'd buy it just to have it around to collect some dust! Good luck

Its not a FM engine. Its a mix of a sampleplayer and a subtractive synth.
You cannot use the filters on samples. But you can use the filter on the square- and the sawwave. So there it will make an addition to your QS6.1, because you should be able to make filtersweeps. I cannot remember how controllers are implemented and thats why I'm not sure of the sweeps.
I also think that its able to do keysplitting
so you could also use it as a controller.
Anyway go to http://www3.bc.sympatico.ca/epsilon/lapage.htm and get some more info

Actually not a bad deal for $200.

With a computer based Editor/Librarian you can create a plethera of sounds as natural or as weird as you like.

I`ll probably get, it thanks for all your input .
I think it will enhance the sounds
I already have in my Alesis QS6.1 plus
be able to use its resonance filter that
the Alesis doesn`t have plus increase the available voices "although 12 bit it sounds pretty clean and crisp"Chodan