I'm 6' 1" 265lbs. The springs on my DRZ400 were definately too soft.
I was able to get sag adjusted properly, but the back end bottomed too easily. With stock suspension I really had to muscle the bike around, which wore me out on long rides. Long sections of really tight woods were just plain miserable. For low speed handling on open trails the stock suspension works fine.
For Suspension work Pro Race Suspension gets my vote. You can find the advertisement in the back of Dirt rider magazine.
Pro Race Suspension is local for me. I got a quick turn around time on the suspension work. When I got my suspension back the sag was set perfect. The compression front and rear was close, about 2 clicks too hard for me. After 6 months with this Pro race setup I am very pleased.