Welcome to the forum - Good choice of car !
Best bet would be to use the search function of this forum as there has been many many topics on the iPod integration. Dension actually manufacture the Audi unit so both work in a very similar way.
Both are, in my opinion, pretty poor solutions as the Audi head unit is unable to show track information. The units basically replicate a CD changer. The first 5 playlists on your iPod are mapped to CD1-5, CD6 is your whole iPOD library.
Individual songs are simply shown as track01, track02, track03 etc
It's not a great solution but it does work and the sound quality is better than the FM transmitter options which is pretty much your only other option.
FM transmitters work by tacking the signal from your iPOD and broadcasting it to a FW waveband which you then tune your radio into. Once again, no track info displayed and if you live in an area with no free FM frequencies then it won't work well at all. You also have to retune the different frequencies if you go on any longer journeys.
I have the Audi iPOD interfaced connected to my RNS-e and indeed purchased it from audi-accessories.co.uk. Recommended seller.