I'm glad I found this thread as I'm considering buying either the Pro or Classic. At the moment I have a pair of Audio Technica ATH-M50's and some Philips Fidelio X1's but I really can't decide which is better but having read some reviews of the Focal's on the Innerfidelity site, they seem like they'll be better still.
What I'm after is a sound that will most closely resemble what it would be like to hear the music in the studio or what the artist heard/intended for people to hear. The Audio Technica's are great closed-back and offer more clarity and detail but can sound a little harsh with treble and high frequencies but the Philips while sounding lovely and warm, are a little more muddy and lower volume and tend to offer lower clarity and detail.
I do the majority of listening on my PC through my Focusrite Scarlett 2i2 audio interface but I don't know whether the Focal Spirit Pro's will perhaps sound too flat and balanced or whether the Classic's will be too warm and muddy? I also make a lot of music for I'm thinking the Pro's could also double-up as my mixing headphones (I use the Audio Technica's for that at the moment).
Of course price is always important and Amazon has the Pro's for £202 and the Classic's for £245.