MIDI USB:
I'm really pleased with my MidiSport2X2usb and have had no troubles so far.
I'm only pushing 4 units at this time though. For the cost, ($60-$70) the midi port indicators are nice when troubleshooting your setup. When I first bought it, notes were not shutting off but it turned out to be the synth midi-in cable wasn't plugged in ALL the way. Duh...
As for Effects, there are some MAC Carbonized and Classic VST effects with Metro that I have really come to appreciate lately.
There are lots to choose from...Waves(beautiful but expensive) to Internet freeware(Some are awesome, but user beware
). Many of the Carbonized effects from the Bias Peak 3 Demo I'm messing with are pretty nice too. I'm still working on that that upgrade....
Kevin