Honestly, try to take our advice when it comes to buying your first track bike! I am telling you now its hard to not get a "better" bike at first but trust me, the actual bike is not what make's you faster on the track (talking about corner speed here of course). I have a '12 S1000RR and a '12 675R (track bike), and now I'm looking for a track bike that I can use as a spare and not care if I beat it up!
It's a 10x better bike when it's set-up for you, and the 675R is sometimes a bitch to get set-up (I'm talking racing pace here though).
What I have found in my first year of racing/trackdays that REALLY make's you a better and faster rider are these part's:
SUSPENSION.. Ohlins 30mm Fork Cartridges & TTX36 Rear Shock
Full Exhaust (not just for power but weight savings mainly)
The cheaper the first track bike you get, the more $$$ you can spend on getting you're suspension tuned for you, and tires.
So, my recommendation would be to definitely get the R6. Liter bikes are fun on the track, but 600's are so much less work and so much smoother. If you got a 675R, you don't need to put as much money into it as any other bike brand new, but still, prepare to put some money into any bike you are making a race bike.
You say you're going to go to only 4 to 6 track days next year, but I have met too many people that got addicted to the track pipe just by going once. Watch