armrest is very easy to fit yourself. It cost me about £190 from vag parts and took me half an hour. It adds to the comfort and also makes the interior look complete.
The highline is in my mind essential. I think the black looks okay on the 17"s, and depending on angle, actually prefer it.
I wouldn't pay extra for the VW ipod kit. It is lousy, gives no track info, only 5 playlists and only allows you to advance the tracks one at a time. There are much better after market solutions. I have the harmon kardon and love it.