Great driving car under $20k

[WSSix]

I'm thinking about picking up another car to drive on the weekends and whenever the urge gets to me. Requirements are under $20k, rear wheel drive or all wheel drive, manual transmission, comfortable(so not small), and great driving characteristics. Preference is for a V8 but a high powered 6 is possible. I also don't want lots of maintenance involved. I figure we have a rather diverse crowd here that's driven many different cars. What are your opinions? No Corvettes. They're great but I want something else.

I've been thinking about 10th gen 5.0 Mustangs, Infiniti G37's, BMW E34/39 540i or M5, BMW E46, and Audi S4/5/6. Emphasis is on driving enjoyment which is why I've listed BMW's since people swear by them in those regards. I'm concerned about cost of repairs of the BMWs and Audis though. Should I be considering it'll mainly be a garage queen? Figure 5-8k miles yearly at best. The E34/39 540i's and M5's have got to be at the bottom of their value curve. They really look appealing as a second car that holds potential to remain valuable or increase which would be a great bonus.

Anyway, I'm interested in your thoughts/suggestions and experiences.

Thanks