YFZ 450 might be another choice for you, Think the last pro xc race, YFZ was 1st and two ktm riders took 2nd and 3rd. If KTM had Bill Balance they might have taken the whole podium. I like the way my KTM feels over the YFZ but I've never been on a built YFZ. So if you count cost ....
YFZ - $6000 to $7000 (depends on if ya get good deal or not)
KTM $9000 to $9500
If you go with KTM you'll probably want to put another $2000 in it.
If you go with Yamaha you could put $5000 into it to get the same cost.
If your not a pro rider and don't require brand new machine then you could look at some used quads and you might find someone put $15000 in it and selling for $6000.
I Really like my KTM but I think it should been more race ready than it was. If you do go with KTM you'll find this site very helpful and there is plenty of people here to help ya trick it out to your hearts delight.
-Voodoo