First of all, your wheels wont work for a Rabbit/GTI. The are 5x112, however the offset is too low and it will look ghetto as fuck, skateboard style. Sell them and start over.
I have had a 2006 GTI DSG, a 2008 Rabbit 5 speed and now a 2009 GTI 6 speed. I have liked them all. The rabbits are such a good deal right now, you can find CPO 2008's for about 12k, and throw on some wheels and coilovers for 2k and be set for 75k miles of warranty. However coming from the GTI, the Rabbit was too big of a step down, so I imagine you will feel the same way coming from the S4.
I would think long and hard about this decision. The B5 S4s are CLASSIC Audi. They will age fantasticly and still look good in 20 years. I would not get rid of it personally, fix it up, and keep it running good until you graduate.
Ask me anything you want about the GTIs/Rabbits. I personally think they are the best looking hatch out there.
http://i611.photobucket.com/albums/tt197/mkvaaron/ugkeskingti2.jpg
http://i611.photobucket.com/albums/tt197/mkvaaron/redvotexgti.jpg
http://i611.photobucket.com/albums/tt197/mkvaaron/blackrabbitwithvotexandrs4s.jpg