well, you only really have 5 "outboard" units, you are running them in mono right? In which case you need something with at least 6 ins and outs. I would aim for 8 in and out.
I guess you're aiming at a laptop else i'd recommend an M-Audio Delta PCI card which are great. I use mine for routing to pedals when we're DIing guitars and bass. Quite often I record a dry track, then feed this out to several pedals, record them all seperately (at the same time), then mix them together in the computer.