Does anyone know of a good sequencing software I can use to control samples from my sp404? I thought I could do it with Reason, but I guess not...How about Ableton Live? I would like something that has a drum machine, if possible...

If you just need something to program MIDI tracks manually and use them to trigger your SP's samples, i'd keep it cheap and "simple" and go for something like energyXT or even Reaper (which is not by any means "simple").

Reason doesn't really send MIDI Out...any other DAW will do it, definitely Ableton. or get a cheap second-hand hardware sequencer if you really want to be