An effects loop on the SPs, so you could send pads that you want through effects without having the effect applied to the other pads that you don't want to have effects on. This would also eliminate the 1 effect at a time limitation. I dunno, it would help me out a lot, personally.

Well at least on a 404 you can just hold the remain button and press the pads you want the FX to be applied to and that leaves the other pads without the effect too. It's still 1 effect at a time.

yeah, same deal with 555, but not all of the effects on it have the settings i'd like to aquire. (IE the reverb controls aren't broad enough for me, there's a lot more I'd LIKE to do with the reverb, but can't because I'm limited by the SPs settings) Being able to use my own effect units would be great and wouldn't limit my use of effects

Ok man, just thought you might not know this. Well that routing would be cool thing to have. but so would a 555.