Wotcha Steady
If you're looking at getting a 910 with HRM you might as well go for the associated Garmin cadence sensor too then you've got everything you need (and swim watch too) all in one package.
I think Polar have just/are about to release a new watch which does GPS/HR but can't remember if it is compatible with cadence sensor. Fairly certain it doesn't do swimming though.
Can't help with turbo. I have one ( Minoura HyperMag 1200) but it doesn't get used as often as it should for some reason 