RH-50 are Roland's low-end studio monitor headphones. In spite of which they're quad-driver - they have dedicated tweeters which sound really smooth when the headphones are recabled. Great for saxophones and any treble-based delicate music. RH-50 are much like the K-240 with less detail and an even more raised midrange.

And AKG K-240 Studio are, well, what the name says - studio-standard headphones. Current generation (4th, 55-mm. diaphragms) is quite different from the original, if you want a suggestion, try to hunt down the original silver K-141 or K-240 Sextett (38 mm. diaphragms, K-240 are the circumaural version of K-141) and recable them, then give them a good amp.

You can mix in K-240 (many musicians mix/record in K-271, the closed variant), and frankly, the stock AKG cable is horrid. A replacement cable might cost almost as much as the headphones themselves, but it's worth it.