I tried out the Vox Amp Plug and the iRig for bass and found both of them to be junk. I bought and kept the Pandora Mini. http://korg.com/pandoramini
It's made for both guitar and bass. It's another product that favors guitar, but it has plenty of bass capability. It allows you to edit the presets. The tone is flexible and very good. It has good battery life - 1 AA. I get a lot of use out of rechargeable AA's in this thing. It's quiet too.