All those stating to buy either a Gallardo or R8 with the V10: You're not comparing apples to apples with the choices he has listed above.
Yes, these two cars sound great and drive great, but they do have a Lambo V10, so that will cost him $1 - $2 per mile driven for maintenance. None of the cars he has listed above will cost that much to run. I'm not sure he'd want the headache of this type of ownership coming from a Merc.
I believe the V8 R8 will be "cheaper" to run than the V10, but they aren't very quick. They do look nice though.
You can't go wrong with a GT3. If you look hard enough, you can find some in your price range:
http://www.autotrader.com/cars-for-s...31553051&Log=0
For driver involvement, this manual GT3 would be my choice. The NA flat-6 sounds utterly fantastic too.
http://www.autotrader.com/cars-for-s...27743295&Log=0
A little over your budget, but with only 10K miles and a manual, this thing will retain its value pretty well.
http://www.autotrader.com/cars-for-s...24434942&Log=0