I have always wondered about the Acoustic Simulator. I like to think of it like the Dan Electro Sitar Swami: don't expect what the pedal says on how it will sound. Maybe it won't sound like an acoustic guitar, but it will still sound cool.
speaking from my personal experience id just buy it to keep it as is. the grabber pick ups imo are crap. i own several gibson basses an the p config would sound the best. if you get that bass for 400 it would be a great deal! original G-1's go for about 850.
i would add a mic to give it more of a full sound.. di only gets your amp,bass and effects depending on the way you set it up. using a mic on your cab will give you the sound that you hear though your cab obviously
if your getting a ampeg 4x10 Do not get a new one. they are crap. get the saint louis music ones. the new ones are made in Vietnam, and are poorly made.