I also ordered a 49 tooth rear to replace the 48. Third gear lugs a little more than I'd like.
Go faster. Or downshift.
Kidding. But seriously, I never quite get complaints or comments like that. If you decide that 5000 RPM is the "bottom" of the scale and 10K is the top, the bike will pull from 32 to 65 mph in third. But it will also pull from 27 to 53 in second. Going from a 48 to a 49 will only change the third gear running range under those circumstances by about .6 MPH at 5K, so it becomes 31.4 to 63 instead. Not sure that will do much. The first three gears in the bike are very close, and there's a lot of overlap, especially being a 4-stroke.
As far as tires go, especially fronts, everyone's dirt is different, and everyone rides differently. Bikes are different, too of course, just not as much so as the other two things. Look at what the really fast guys in your area are running. Bridgestone M203 did it for me; couldn't live with the MX31/51 in front.