Great question. The simple answer is that, I've always been kind of "meh" about the Quilter preamp, and was looking to bypass it completely by running a different preamp into the Line In.
However I think I've flip-flopped my opinion within the past 24 hours. Last night I went to a blues/rock jam. I've been playing with these guys for ages, so they are familiar with how my sound has evolved through the years. The feedback I got from my friends was superlative: they said my tone through the Quilter was, without a doubt, the best my bass has EVER sounded to them. My conclusion is, the tonal qualities I don't care for at bedroom/practice volume, those same qualities sound great cranked up in a band mix. I'm still finding the preamp section to be not particularly user-friendly, but once I took a little time and dialed in that "sweet spot" it was amazing! So maybe I will put the preamp search on hold and keep exploring the sounds I can get from the Quilter.
P.S. I think another reason the mix sounded good last night is that the guitarist switched from a Fender Twin to one of those little 5 watt Bugera combos. By lightening up his guitar tone, I think he also inadvertently helped my bass sound better!