Andrew Rieger
500+ Head-Fier
Since you like changing gear every few months I suggest a used EL8o or HE-400i, both are relatively easy to drive. If I were you I would get the HE-400i and spend the difference from the EL8 on a decent amp, that way you would also be able to use it on your r70x. For flexibility I suggest a amp from Garage 1217, some of the more flexible amps around and will not break the bank.
I just picked up two Nuforce HA200's to run in monoblock balanced mode with a TEAC 301 DAC so I should never have power problems in the future. I just like trying out new headphones and while I like my R70's, I feel like its not an endgame can and I can do better. The problem is that there are few options between $500 and $1000. I want an open can with good detail but a decent amount of bass. I know the 650's are 90% what I'm looking for but I just know the bass will be a disappointment. I'll probably just get the Omni's.