I considered an after-market - but I like the remote controls and Multifunction display so decided to stick with the standard fitment. (I have a CD Changer 'that doesn't work' and a Cassette !)
Also with a JBL Amp to sound quality is good, although these were only fitted to D9's (although I stand corrected

) From what I was able to find out, D9 with JBL can be tricky unless you disable it (but check it out on the site, the guy's have a wealth of knowledge are are very helpful!)
If you want to use the MFD and Remotes you will need a Head Unit that supports 'Sub Display Out' (for the MFD) and Remote 'Connection' (usually via a 3.5mm Jack Plug), but this means a more expensive Unit?
I looked at a Pioneer at about 140 New (£50 on Ebay) with Autoleads adaptor (£12-18) there are more sophisticated options but they can run to over £100.
D8 is more straight forward, I put a Sony in my old D8 Estate which was pre-JBL Amp, worked very well with good sound quality.
For D9's the CD Only Head Unit was a
RD2 and you can pick them up on Ebay for about £30-£50 - but it will need re-coding.... hope it helps
