I'd suggest you take your bike to a shop that has a dynamometer and find out at where your bike starts to lose horsepower or torque. On my '97 M900, both torque and horsepower begin dropping off at just under 8k rpm, so there's no real need to rev the engine past 8k. If my bike didn't already have a tachometer and I was shopping for one, I'd opt for the 9k model--the righthand side of the 12k tach that the PO of my bike installed is wasted space and doesn't even score any poseur points.
Sorry, I was wrong, my tach goes to 10500 and redlines at 8500, dont know why I though it went to 12 but after the ride to work this morning I noticed I was wrong.
It was an after market one that uses LED lights in a semi circle, not sure who made it.