Or better still, BT14s. I've had a pair of these put on the 900 and they are very confidence inspiring (and I'm a coward). Had intended to have new Bt10s in the light of my experience with the 620 but was told that the BT14 was the replacement for them.
Don't need to spend that much on tyres for the 620. Stick with an 010 front but put an 020 on the rear. Got fantastic grip and longevity on my 750ss with that combo in the rain and dry, all year round in fact