I'm also considering those Falkens as my next set of performance tires -- they seem to have an excellent grip/expense ratio, and reputedly work well in the rain as well (this is a factor in WA state).

As for the speedo error, it's very easy to change out the drive gear without removing the tranny from the car. Various ratios were available. If your speedo reads high, you need one with more teeth than what you have now.

What I don't know is whether or not these are still available from Volvo -- five years ago they were, but ???