Think you may find that's the fastest CPU the board will recognise. If you have the latest BIOS update, then you can go to a 2400 or even a 2600 but of the Thoroughbred model and these are starting to be a little hard to get hold of now.
AMD have moved on to the Palomino core and higher.
I have the same board and did have the 1800xp CPU, just managed to upgrade to a 2400xp a couple of month back and it was hard to source the chip then. To be honest, I have not noticed any difference and think you will need to make an increase of at least double your present CPU to gain any advantage, but that will mean a new board as well.
click here and look under products for your board and under downloads for the BIOS up-dates. There are 2 versions of the board, and you will have to look at the board itself to see if it's a Ver. 1.0 or Ver. 1.1 Regards. j.