Depends on a number of things, I guess, but I'll say what I got and why, which you might find helpful.
I got the Kenwood KDC BT61U. Paired with Infinity reference speakers front and rear.
I believe it has now been replaced by a newer model KDC BT92SD which looks identical to me, but I assume has more features. (...Yes, it now has an SD card slot.) The old model should be available for a while and you might get it for less than 150 quid now.
Like you, quality rather than size of sound is important to me. I would say however that after 9 months of listening I am considering an underseat sub to fill out the sound a little as it can become harsh when cranked up, so a fuller sound a lower volumes would be my preference.
This has the major features I was after: bluetooth (i)phone integration; a REAR ipod connection so you can hide all the wires away, and the ipod in the glove box; a further rear stereo jack in, in case someone wants to throw a generic mp3 player at it; standard ISO connector which should fit the coupe assuming nobody has butchered it to put in an old pioneer or something.
It also looks sleek, and tart that I am, I quite like the fact that you can set the button illumination to match your dash strip (unless you drive a crono), and the screen illumination to match your instrument panel lighting.
