i'd think about upgrading your stereo to the Alpine INA333 (something like that) under £1000 but you get top quality HU, DVD maps of most of Europe, TMC, which you won't get on any PDA! MP3 changer is just over £100!
I tried the PDA's the cold locking could take an age, they were a lot slower than Alpine and the Alpine is 1U, can work fully with MFSW!
www.mcs-direct.co.uk for the best prices!!