My 335xi is up for sale. (Not looking to have a BMW vs Audi thread please) Looking to get into a cheaper daily driver & add a C6 Z06.

Have been hoping to find another Mazdaspeed6 GT to buy, but growing impatient & frustrated with not finding the right car or the right cars being sold before I can get to them.

Pretty much looking to keep it in under $20k for whatever I get. The $15k area would be ideal.

I've driven 2007-08 & 2011-12 S4s. have loved these things for years. Just read/hear about so many folks saying do not own one out of warranty, they will break all the time & cost a fortune to fix, electrical gremlins, etc etc.

I'd be buying a 2004 or 2005 it seems if I went w/the 4.2 V8 variety. Would not be opposed to getting the previous gen w/the turbo V6 either, but I am looking for something that will be reliable & not cost a fortune to maintain & that I can work on myself if need be.

So what are the big problem areas for the S4s?
What options were available on them?

TIA!