Can't answer this. The preamp does not exist in a vacumn. You need to think of the whole system that makes the sound as a single system, not a series of independent parts. That would start with strings, then instrument, pickups/mics, cable, preamp, amp or mixer or powered mixer, PA, speakers.

Take every existing part of your strings-to-speakers system to the best music store you can get to and then experiement around with different items that can make your instruments sound good. I have an 88 ovation with built-in pre-amp that sounded kind of thin and tinny and I thought I needed another more robust pre-amp. When I took the kit 'n kiboodle to the store and started experiementing, it turned out I only needed a $90 transducer plus a little more digital delay in the powered mixer, but neither the transducer nor the extra DD sounded particularly good on their own. There are some pricey black boxes that will do everything for except strike the strings, but you may not need it. Trust your ears and Good Luck!