Pro900's are awesome and can be found used. Worth whatever. Love mine.
Denon D600 is another great over ear basshead phone I own. Love it as well.
Not sure about the Ohm spec....you need portable?
Definitely the #1 can I recommend to people. A great all-rounder.
I just heard the midrange is a bit laid-back which isn't to my taste, in a Signature DJ vs Fostex TH-600 comparison, the Signature DJs were even said to be slightly more forward sounding and that headphone is also said to be a very slightly bit recessed in the midrange by general concensus which makes me worried how TH-600 is. Maybe it isn't a problem for you like it probably isn't for majority amount of people as people tend to like a minor V-shape pretty often but for those people who like a more intimate/in-your-face midrange it may be a prob though.
What I'm trying to say is that for most people it's enough that the mids sounds clear (which they do with emphasized highs) but I personally want up-front sounding mids (the feeling of the vocalist just standing next to me) which I wouldn't expect to get in TH-600.
Another thing that can be a problem is isolation, these doesn't isolate well from outside noise. Lack of isolation and midrange laid-backness is probably the most noteworthy aspects that may not be good things to everyone. Most other things it probably does handle well though. :)
Those are very different from your current cans. Nice move. Buying another bassy set for 100 woulda been a waste of money. Might as well experience another kind of can. Again...good move. Congrats and enjoy