Just to update this thread with my own reply, some two and a half years since my last post, I can report that I now own two (2) Icon 5s - one fretted, the other fretless - and they are every bit as nice as I'd hoped.
FYI, the stock Icon pickups & preamp, however, are long gone. Soon as I could, I upgraded each Icon with a set of SGD wide-aperture N3 Neo humbuckers, along with an Audere 4-band onboard preamp with "Z" switch.
Wow. What a match made in heaven! No "nasal" quality or "honkiness" to the tone anymore, that's for sure! Nothing but deep, phat, hi-fi smoothness!
Side note: I've finally played the GraphTech Ghost onboard piezo system that Roy mentioned...though I had it installed into my new Bromberg 5 fretless instead. Only difference with the stock Carvin configuration is that mine has a separate piezo volume control - rather than the pan pot that comes standard.
I rather like it - though as Roy said, a little goes a long way. I use it mostly to mix in a little extra high frequency - to add a bit more hi-fi clarity to the magnetic pickups on certain lines. I haven't yet found an application for a 100% piezo signal, though I'm not ruling that out. For me, it still sounds best when blended - sparingly - with the pickups.
MM