You could use the alternate cable routing to use the 9 speed cassette with the 10 speed shifter..

I've used a 6500 crank with a 6600 front derrailleur, but I did need a 10 speed chain on that derrailleur. This was done with 6600 brifters and 105 cassette, I had no shifting issues. I also ran with a 9 speed Tiagra setup, with that crank.

I have a buddy that used the 6600 shifters with a 9 speed cassette and the alternate cable routing, so I've seen it work. Sheldon Brown talks about it.