Look, there is no way to balance the different unnatural qualities of various headphones on the same level.
At the highest level of HD800, LCD2/3, better Stax and so forth, the differences are more down to taste (yes, these are out of your price range, but the same applies to sub-$500).
What you want in monitors is consistency, predictability, versatility and articulating factors. Then you just learn to listen to them, learn their failings and adjust accordingly to the natural unamplified acoustic sound.
With this in mind, some of the ones I've listened to and which I would consider for final mixing/mastering would include:
Closed circumaural
- Beyerdynamic T70 (can be a bit harsh, but extend well, articulate well and isolate beautifully with the gel pads you can buy separately)
- ATH-M50, basic cheap tool. Good enough. Not at the level of T70 in articulation and separation, imho, but you can use these as do many pros.
- Sennheiser HD650 (why you may ask? For really extended sessions, even those these aren't most revealing, they are very comfortable to listen to for hours to an end. Just learn their shortcomings)
I could recommend the AKG 701/702 as well. The bass is just harder to track on those, it's just so low in amplitude. But like I wrote, you can mix well even with these. Just know them.
Personally I think the Ultrasone's are just a design gone horribly wrong. Yes, you can get accustomed to them and mix on them. Many do. I just can't stand their house signature sound. YMMV, of course.
People have done colour correction on black&white monitors and mixed very good records with lousy Yamaha monitors back in the 70s. Everything is possible. Just learn your tools inside out and learn to go beyond their limitations. You are what hears. Not the headphones.
