The Lexicon Lambda is ok, but it's nothing like an Apogee. You would hear a big difference even just playing mp3's in iTunes!

As far as midi and keyboards go, just remember that the keyboard you use will just send a command to the computer to play the "Patch" that you selected. Your choice is to either use a Keyboard with built in sounds and plug that into a mixer, or use a keyboard controller to play softsynth sounds in your computer.

One other option I recommend and should have mentioned earlier is a Program called "Reason" by Propellerhead in Sweden. It has taken the music world by storm. Wonderful sounds, you start with an empty virtual "Rack", and then you fill it with synths, samplers, drum machines, effects, mixers, etc. Go to Youtube and type in Reason 4". That should at least give you a chance to understand what it does. And, you can use it in your DAW program using a protocal called "Rewire". I know it seems I'm writing Greek Math, but by watching the videos you will learn quickly.

Ed