is the m-audio keyboard the 61 key evolution? if so, i have that model and am very satisified with it. I was in a similar situatio as you where i wanted ot use softsynths to play, so i didn't require the speakers. I also like the ability to use USB as a power source for the keyboard, it's great for on the go laptop music. Programming it can be a bit tricky but not undoable.
one thing to be careful of though is that make sure you have a decent computer and soundcard to give you a low, clip free, latency. Anything over like 5-8 milliseconds will be noticable when you play. By this i mean that there will be a slight delay from the time you hit the key to the time the sound comes through the speakers.... very annoying.
MME drivers will not work but ASIO and WDM probably will. I have better luck with ASIO than WDM though.