Are you in an area close to any of the local meets?
When I was ready to take a step from $100 HPs to the next level (had a ceiling similar to yours), I was lucky enough to get to attend Can Jam09 in LA. I listened to a dozen or more HPs I had heard of or seen mentioned on here, or just discovered while walking around. (I ended up going from AT ATH700 to Denon D5000). Then when I was thinking of taking the next step up, I was once again lucky enough to attend a local head-fi user meet. There were around 40 of us and there was a wide range of mid to upper level HPs (HD800, T1000, D7000, LOTS of Stax, etc.) and I was able to listen to every one of them.
So that helped me immensely because I was able to take people opinions on HPs I had heard myself with a grain of salt and it taught me just how varied people's tastes are in sound, and I find what I like this year, may not be the same as next (I went from D5000 back to the AT line, but up to the ATH-W1000X this time). I thought I was a bass head and I loved the D5000s for about a year and my taste changed and I wanted something different. I don't think of it as a vertical progression, I think of it as a lateral movement that emphasized my tastes in this period of time.
I also have a couple of friends that have AKG and Grado's and they are nice enough to share, as I do with them, and this helps a lot also because I can audition them for a day or a week at a time.
I find the opinions on here are great, and I love this site, but in the end it is musical tastes that must be served. But that is my adventure, and my opinion only, and others may disagree. That's whats nice about this site, and also that's what bites about this site. It should not be your conscience, only a guiding light...IMHO!