Sports photography lens setup?

I'm a beginner sports photographer and I need some information on lenses.
I see videos and pro's at games using 400mm f2.8, but I have a Nikon D300S so a 400mm is an equivalent 600mm which I think is too long for football (soccer) photography (mostly).
Which set-up would be better for sports?
1) Sigma 120-300mm f2.8
2) Sigma 70-200mm f2.8 and Sigma 300mm f2.8 and a second D300S

If you have any other recommendations then please include them in your comments

I use a 300mm f/2.8 on a Nikon D3 but my pal uses a 400mm f/2.8/ on a Canon 1DMk2 to good effect.

I'd go for option 2, although I prefer Nikkor lenses.

How about a Nikon 200mm f2+ teleconverters?