Hi there,
A little more than a year ago I struggled with the same problem. I've tried several effectprocessors. I found the Lexicon LXP-15 a pretty good option, but that had a dip in the sounds when you switched the effects. Finally I came across Line6 Bas Pod pro. It isn't the best preamp, compared to the Alembic preamps. But it has some fine effects onboard. Like: mutron, distortion, flanger, phaser, chorus, octaver etc. Another advantage is the fact that you can make your own presets with diferent preamps, so can can change your sound totally with a little tap on the floorboard. It's a really nive toy to play with. Though I must say that the onboard effects are not so good as the original effectsprocessors. But then again, in that case you would end up with an effectrack which is almost 24 HE...... And that's a lot of knobs
Good luck with your search, keep 'um grooving
Mattheus tDo