The stock Volvo pads for the US market are about as soft as you'll get, as they favor the first stop over fade resistance (driven by US safety standards). They are also about the quietest pads available, but I doubt you'll find dirtier pads anywhere.

I understand your thinking for the track, but on the street you won't be torturing your brakes like on the track. I drive pretty aggressively, and my front rotor life is about 90K miles with hard PBR Metal Master pads. Pad life is roughly half the rotor life.