I think that power is more of a preference than a necessity, with respect to speed. I recently road some tight, open and everything in between singletrack near Steamboat, CO with a guy on an EXC200 and, wow, was he fast. Let me put this into context. I'm 6'2', 180lbs (without gear) and ride a yz250 with an 11oz flywheel, custom suspension, etc. Plenty of power and it is certainly faster than I am. I ride trails very quick and even get compliments on my speed and cornering. I am always in the lead group, leading or closely following on trails (I'm a total puss on a track). Anyhow, I struggled to keep up with the guy on the EXC200, who was very close in height and weight to me. It was the first time I struggled to keep up with anyone on a trail, ever. This guy rocked. The point being is that, with certain exceptions, power is almost irrelevant on singletrack with lots of twists, turns and features. The guy on the EXC200 was fluid and consistent through everything. I could out accelerate him, but that didn't matter. His ability to handle the bike and maintain speed made him fast, not the power or acceleration. I capitulated between the 300, the 200 and the 250. I bought the YZ because I got good deal on it. I absolutely love it without complaint. That said, I may look into a 200 for my next bike.