I've got a set, I like them very much, the only issue is that they're a little bass heavy so you end up pulling it out of your mix more often than not. Totally worth the money though, they sound just great.
Headphone amps: worth it as well. I have an older Rolls 6 channels one that works alright, if you can find the model numbers of the headphone amps that used to come with mixers in the 70's those are the best and way cheap, but for a cheapo single headphone amp figure on about $40, which isn't terrible.
cheers,
scott