Now that I've replaced the horrid rear speaker, I've actually begun to enjoy the stock Blose system in my C5. The fronts aren't too bad, actually, but the settings on the Head Unit are critical. First, any kind of EQ, even Classical, which is supposed be flat, just destroys the imaging and accuracy. I've gone through and reset everything, including radio stations (which have individual "tone control" memories) for the non-eq position, which is represented by the blank screen where the EQ curves pop up. That EQ is nasty.
Next, I played with Bass, Treble, and Fade to get the best sound from the system. I used a variety of audiophle-class CDs to get the best compromise for all material. With my stock unit plus Pioneer 1664's in rear, I find most accurate and pleasing sound with Bass just below 12 o'clock, Treble at about 4PM, and Fade set at about 10 - 10:30 AM. If your rears are more efficient than my Pioneers (92 db) you may be able to crank it more towards the fronts.
Anyway, the system now is at about 90 per cent of my best car audio system, which is really very good. Voices sound great, instruments are correct, and the bass if improved and not as muddy in the 60-120 Hz area. There's little uumph below 50 hz though, coming from that Blose subwoofer system. Best bet is to tone it down to where it just begins to be obnoxious, just left of center.
Posted for those who care about good sound (as opposed to thump and sizzle :D ) and want to save money on the audio. I really like listening to my Borla Stingers, best anyway! ;) :cheers:

 

I thought the Bose speakers were amplified? Is that just the fronts?

The stock unit in the Z06 does not sound as good as what I've had in my Coupes. The rear speaker appears smaller, at least the grill is.

Wouldn't mind a swap, if it's just a matter of changing speakers out.

 

See: http://forums.corvetteforum.com/zerothread?id=285992

That has a lot of good info on the Delco/Bose system in the C5. I think the fronts have some small amps; rears just have the speaker wire going to them. I think the Vert and FRC have 5.5 inch, but the coupe has the 6.5's. Might be able to squeeze a larger speaker into the 5.5 inch holes, not sure.

Good luck,
:cheers:

 

Thanks, great info, much more than I know how to use.

Looks like 4 ohm 5.25 speakers should do it.