If you're lucky enough to find a korg ax3000b on ebay or craig's list, I'd say go with that. it has great sounding filter effects. I've recorded sound samples of the korg ax3000b on my soundclick website. feel free to check it out. here's the link.
www.soundclick.com/crystalman85
If you're unable to find the korg ax3000b, the zoom b2.1u would be a good choice. they got some decent filter effects.