The BMW E60 M5 isn't the V10 bargain it once was. As clean examples have become harder to find and enthusiast interest has grown, the legendary sedan has moved well beyond its affordable performance-car days. But sitting beside it is the E63 BMW M6, sharing the same 5.0-liter naturally aspirated V10, 500 horsepower, rear-wheel drive, and a chassis built around BMW's high-revving S85 engine. Produced from 2006 to 2010, the M6 came as a Coupe or Convertible, with a six-speed manual alongside the seven-speed SMG.

So why hasn't the M6 received the same attention? Part of the answer is obvious. The E60 M5 was the practical super sedan, combining four doors and enough space for daily use with an engine that revved beyond 8,000 rpm. The M6 was something different. It was a grand tourer, with two doors, a long hood, a more dramatic shape, and a cabin designed for covering serious distances rather than hauling the family around.

Mechanically, though, there is a lot less separating the two. The M6 gets the same S85 V10, the same rear-wheel-drive layout, and essentially the same powertrain character. With individual throttle bodies, a naturally aspirated power delivery, and an 8,250-rpm redline, the engine is the main event. It doesn't deliver its performance the way today's turbocharged BMWs do. You have to work for the power, and that makes the experience increasingly unusual.

The M6 also has a few tricks of its own. The Coupe received a carbon-fiber roof to help lower its center of gravity, while aluminum body panels and other weight-saving measures helped offset its substantial size. It was never a lightweight sports car, but BMW's goal was to make a high-speed GT that could still behave like an M car when the road became interesting.

That makes the M6 particularly appealing now that the E60 M5 has become expensive. You're essentially looking at the same legendary V10 in a rarer and more distinctive package, with the added possibility of a six-speed manual. The M6 never had the M5's cultural cachet, but that may be exactly what gives it an opportunity today.

Look at where the E46 M3, E92 M3, and E60 M5 have gone as enthusiasts have become increasingly interested in BMW's naturally aspirated era. The later M6 went in a completely different direction with its twin-turbo V8, leaving the E63 as the only M6 generation with the S85 V10. If the E60 M5 is no longer the bargain it once was, the forgotten M6 may be one of the more interesting ways into BMW's V10 era before everyone starts looking at it the same way.