If you can still get M5's - grab 'em!
I tried the new M7's last year and they were no-where near as good as the M5's. In the end, I managed to find some new/old M3's and put them on in an effort to regain what I lost but haven't had any seat time on the yet.
On the 600 I'm looking at getting Dunlop Q3's - even though they are a bit long in the tooth now a lot of folks still swear by them and I spoke extensively with a fella that tracks the bike and it sounds like the Dunlop Q3's are very close to the M5's. So that might be an option if you can get the in 110's
I would never ever run any of the tires that 99.99% of the 125 owners run. They're crap with a capital K. Good to hear you post up about it because proper tire choice is vital to not crashing. Aaron's been behind me on a Buell Firebolt (?), a CBR 600, my nephew on a R6, numerous other high-end bikes, and not one of them could ever touch me on a corner. This was due to the tires. Obviously, when your tires stick like that they are a LOT safer then the bias-ply crap the bikes comes with.
Oddly, in all the time I had this site only one person ever installed the recommended tires on his bike (and even then, the touring model). Yet, I've seen lots of posts from folks that crashed complete with pictures and when I look at the places they crashed they never make sense...unless one takes into what kind of tire they were running. With the M5's they never, ever broke loose even when doing 140 KPH through 80 KPH corners (or better). They also save my life in the rain many times.
To me, putting good tires on a bike is a bit of a no-brainer. I've seen quite a few people that are not racing, just touring, that insist on putting on street/track tires just because they would rather have the traction when they need it and will pay for the shorter lifespan because of it. In other words, they want to live and if costs them more tire changes, so be it. I think those folks are pretty smart. They don't use even a fraction of what that tire can do but when something arises unexpectedly, they're there.
The stock tires on this bike (IRC's) nearly killed me 3 times in the rain on one trip. When I saw that (I was new to motorcycling at the time) I spent a lot of time researching tires and that's how I came into the M5's. I nailed it first time out through a lot of research. The fact that they literally stick beyond the bike's ability to break them loose, is a really nice bonus!