the ktm 450 engine is pretty vague, they are different for different bikes
the aprilia 550 can be fairly easily tweaked to 75hp, ron hamp got a crf450r to about that power output for the stock bore/stroke.
the aprilia is illegal to race in AMA, they outlawed twin's. gee i wonder why.
with alot of money, a wr450f can beat an aprilia rxv with a muffler, look at the xgames, it was the yz450 that beat it in smr.
where is this rxv at the e2 last man standing. its pretty much a smr bike, sxv, turned into a trail bike, rxv.
I was going to get an aprilia, but there forks come from a company well known for bicycles, they aren't able to be raced here yet, and they are unproven in enduro racing.
ktm then bmw in that order have the most dakar rally wins. btw