I also used an old mmt8 back in the day. The psr works nothing like the old alesis. But then it doesn't have to. The alesis had such a low ammount of memory to work with that linking/repeating patterns (reccorded passages) was needed in order to conserve memory. It did have other advantages as well, but if you get into computer sequencing you will be much happier than you would be with another alesis. There are many good programs out there both expensive and more reasonable and even free. The free ones will do most of what you would want, and you can always upgrade as you learn more.
Good luck,
Jim
ps I do own the s900 and am very happy with it. Whatever you record midi files on you'ld still want to play them with a dec ent sound source. A module or a great board like the S900 will have fabulous sounds compared to all but the most expensive computer soundcards.

[This message has been edited by OldNewb (edited 09-02-2007).]