nikki,
When I first started riding my 125sx, I too felt it lacked alot of bottom. But I realised that I just needed to ride it differently than my yz125. Although it does lack the bottom of the competitor bikes, it is very managable. You just need to have a different style with the bike. It responds well to clutch slippping too.
I would not trade the unmatched power and mid-top performance of my 125sx for any other 125.
Yamahaman_2k....the KTM won't need mods to be fast as anyone else, but you will have to do some tinkering (soft seat foam, maybe diff bars, susp. work) to get it to be a comfortable bike for the woods. Plush, they aint.