I don't own a Crossfire roadster so can't say for sure. But the Basslink in my Wrangler (yeah, I know, apples to oranges) is very audible and clean.

That's surprising because it's installed inside a small compartment way in the back of the vehicle - the only lockable space on the whole vehicle. There is no air passage to the seating area and yet you can here that sub just fine.

Remember, the low frequencies are not directional like the highs. Lots of subs get installed in trunks and sound great.

If you can find a way to try it before you buy it, that would answer your space question and the sound question. Don't forget the Basslink products have dedicated built-in amps so they're going to have plenty of power to make the sound.

Check the reviews on Amazon - there's a customer who installed it in a convertible (I think it was a Miata or something like that) and was very pleased - even surprised the stereo installer.

Just my two cents