I’ve spent quite a bit of time researching headphones as I travel a fair bit. HD-650 are my personal fav without additional correction software. Sonarworks have reviews of headphones on their site btw, they which are quite good.
I use these two setups for mixing:
HD650+ Sonarworks +Canopener vst appox cost £450
Or
Slate VSX + add on studios appox cost £350
Pros to HD650 setup + vsts: The HD650 are an high quality pair of headphones with or without correction and will last years. Sound ID can be used with other headphones (for example a closed back reference pair like the M50x).
Pros to Slate VSX: There is some weird magic going on with these headphones/software. They emulations are really good. The quality of the actual headphones themself don’t match the price point, but I guess you are paying for the software as well but they aren’t worth it if you use the headphones without a computer.