I had an impossibly perfect 95 M3 with only 5,400 original miles when I bought it. Great car. My gripes were the lack of a 6th "overdrive" gear and the "sedan" type feeling (despite my care was a coupe).
I would have opted for one of the 80 or so 1995 LTW that made it to the States. However, I had to have air conditioning. Plus I liked the Dakar Yellow I paint and leather included on the M3 I bought.
I had the E36 M3 for about five years (put a whopping 1,800 miles on the car). During that time, I had several other 5-speed Porsches (e.g., late 80's and 964s). Difference being, in 5th gear on the freeway, I liked the sound of the Porsches; and felt the M3 was "buzzy" by comparison.
I was going to swap in a Genuine BMW 6-speed at a cost of nearly $5,000. However, modifying a 7,000 mile original example and spending that kind of coin didn't make any sense (I'd be spending money to make the car worth less when it was time to sell).
If I was a die-hard BMW'r, I'd buy a prisinte low mile 95 LTW, add air conditioning and the euro Genuine BMW 6-speed tranny. Of course, we're now broaching $40-50,000. At that amount, there are too many other cars I'd like to have.
Not at all in the $15k range, but my two favorite "modern" air-cooled 911s are the 964 RS America and 993 C2S. That said, my favorite 911s "period" are the 1989 3.2 examples naturally aspirated and 3.3 turbo models (such as the Speedster, Silver Anniversary Coupe and 930 Turbo with that-year-only 5-speed G50 tranny).
Recently considered a NSX. However, the owners are WAY too proud. Pricing is absolutely ludicrous. Exceptionally nice late model examples are in Ferrari 355 territory.
my 2 cents,
Porsche