Hi Willy,
All RX's that are UK spec are AWD (4 wheel drive) so no worries there!
If you want Bluetooth, you need to get a '56 plate car as it was built in on most models, think SE and above. Be warned that Bluetooth compatibility between newer phones and the car gets worse the older the car gets.
In my opinion, the early Mark Levinson (at least on 2003-2006 cars) is OK but not great.
Sat nav can only be updated to a point before you can't get the latest discs with new roads on.
You can get a nice after market head unit with reverse cam, sat nav, dvd playback and better Bluetooth support for about £300 quid or so. Bearing this in mind, an SE or LE that has the options you really need, ie: power boot/tailgate and AFS/HID lights and leather seats - would be cheaper to allow you some spare budget to upgrade the audio system!
I went SE-L cos I actually like air suspension, but them I'm nuts!!