Re: piezo bridge.
depending on what piezo you buy will determine if you need a preamp. i have an lr baggs x-bridge on one of mine with a control-x preamp. i find the preampp unnecessary. its more of a blender circuit and less of a preamp, altough it does have a variable gain boost pot. the next couple of piezos i get will be without preamps, and i will be able to a/b the setups.
the versatility of the piezo is immeasurable. they are excellent and i will be putting in at least 3-4 more in my hardtail guitars. most notably my rg321mh.
as for output...keep in mind that you will more than likely be going to a different output for the piezo, so you can adjust the level seperately from the electric signal to get a better mix. and yeah...it can do rock, but there's not an overwhelming amount of acoustic in rock. its just nice to have it.