First off - you'll get a much better response if you ask that questions on
http://www.q3ownersclub.co.uk/ - plenty of RSQ3 owners on there.
The main think is to check the service history and other "ancilliary" service items. For instance the plugs need replacing every 20k miles or 6 years (whichever is the sooner) and costs about £130 (as you can only get the plugs themselves from Audi).
Also do check the wear on the front disks. Very tight tolerance for replacement, new disks are 34mm and need to be replaced when they wear down to 32mm - roughly every 30k miles. Expect a bill of about £1,100 for new front discs and pads. 2mm wear on discs may not sound a lot, but consider they are vented discs and that is only 1mm per side. And 2 sets of pads in those front calipers as well.
S-Tronic oil needs replacing at 40K miles (latest) - another £120 bill
At 3 years, the Haldex oil and Brake Fluid needs to be done - another £250
If it has a Pan Roof, then this needs servicing every 2 years (greased up etc) - check it was done at 2 years.
Just check the service records (they are on the key but there should be a print out in the service handbook or, if you get the VIN number, put that into MyAudi and you can check online).
Not trying to put you off (I do own a F/L RSQ3) and the outlay is worth every penny (IMO) as its one of, if not the best car I've ever owned, but do check those service items before buying else you could have a large service bill at 3 years old. I've had mine 2 years now, and generally sell my cars on after that sort of time, but this one I'll keep a few more years. And Misano Red for me is the best colour for them (which is what colour mine is)
In terms of options, must haves to me are:
- LED Interior light package. Comes as standard if you have the Pan Roof, else its an option I believe.
- HDD Sat Nav works much better than the SD card Sat Nav plus you can get Audi Connect on it
- Bose system for the stereo
As I say though do try the Q3 owners site, plenty of useful info on there
