interesting and eternal topic...the bane of all guitar users the world over...how do I project what I hear out over the PA.
when it comes to solo or singer/songwriter, a poor pickup can definitely make a good guitar sound like a piece of laminate, but conversely, a good pickup is restrained by the limits of the guitar.
I was at a gig last night, just 2 guitars, yamaha compass and avalon A32 and although the Avalon is head and shoulders above the yammie as an acoustic, there was no magic when it was plugged in and the yammie fit the bill much better as they are engineered as live guitars with the pickup being an intrinsic part of the design, tying directly to Roby's quest and explaining why Tommy "Enamel" chooses to play a deadwood guitar, he's effectively playing the pickup, not the guitar.
I would recommend you try out the new breed of undersaddle transducers that are based on condenser mic strips rather than piezo.
I have a schertler bluestick, expensive, but much more natural sounding.
Little more feedback responsive, but a soundhole cover can go a long way to taming that.
B-band's UST/AST combo with a dual input pre also sounds pretty good and has got pretty good reviews.
for situations where you can't really hear the guitar and just get a chugga chugga rhythm to "cut thru the mix" (takamine/taylor), a bog standard fishman undersaddle normally does the job.
the quest continues....