I've never been a fan of anything under Senn 600's. I've tried the 555/595/598 and they had this really artificial sound. Sennheiser 650's are very smooth and laid back. Anything you play on it will sound good. The downside to this is some music will not sound 100% accurate. Audio Technica 50x, let me first say I love the company but I really dislike the 50's. I put them on and they felt uncomfortable. I'm sure with upgraded pads they would sound decent. In stock form they were un-listenable to me. The sound was very muffled and the bass was overpowering. I purely listen to open headphones so my experience might have more to do with open vs closed then the quality of the AT50x's. AKG 7xx: This really is a "to each their own" headphone. I understand that some people will like this sound and I am not one of these. For me it felt like listening to a 300ohm headphone on a 50ohm amp. The bass was completely lacking and sounded lifeless. I listened to the akg 712 on 3 seperate dac/amp combos and I felt the same. With bass boost turned on they gained a little life but I know this headphone just isn't for me. You might like the out of production denon 2000's. They have amazing soundstage, are closed, and have the ability to make deep rumbling bass or analytical depending on your amp/dac combo.