Standard Philips is not liked. No one seems to have used the JVC judging by the lack of replies. I am very happy with a Kenwood 5080R CD head unit £150 (didn't bother with changer), but if you spend more in the Kenwood range or get one of the fancy OEL display Pioneers you would get more preouts, inbuilt adjustable filters, 4V preouts etc etc. Depends on how far you want to take your system. I miss the speed dependent volume control, compression and clip settings off the Ford head units too - have not yet seen similar in aftermarket units.
I have ripped out all of the factory speakers, currently Kenwood 160mm coax (£72) in fronts (soon to go to back off HU as fill) and be replaced by Infinity Reference Components (£88).
Kenwood KAC848 4 channel amp £160 - good VFM fairly powerful, but you'd end up wanting Phoenix Gold, Rockford Fosgate or Soundstream probably
All really depends on budget, for £600 I have a system I am pleased with and with the new components should be happier still. It is certainly very loud partly due to a monster dual bandpass Pioneer sub box that despite only 8" cone, 100WRMS and £70 absolutely rocks for SPL (claimed 129dB at rated power in-car - only 10dB off pain threshold - but not very subtle!). It was the real bargain of my install, but you need fronts that go to 80Hz or lower otherwise they're swamped by it. Prefab or any bandpass designs have a bad reputation as they are notoriously difficult to get right and are sensitive to very small changes in box construction, and are sometimes billed as "one-note" boxes that just resonate in a narrow band to get their high SPL. I must have been lucky with this Pioneer then!
For £150 head unit and £90 components you could prob. have something that would be good enough for most people? Anyone else agree? Amp and sub will up budget and installation comlexity by a great deal, but the sound escalates to another level. Headunit is a 10min job to change (although some have taken longer because of various problems). Front speakers take a few hours to get right, soundproof etc, but if powered off Headunit would be reasonably straightforward only requiring two screwdrivers and a hairdrier and possibly a junior hacksaw to trim the splash guard.
ScoobyDoc's system sounds very very sweet, but not overly loud. Depends on what you are looking for sound quality or volume
I've not (yet) heard anyone else's system, but it sounds like there are some real amazing ones floating around Scoobynet. You should have some interesting opinions below...