D70 and lens for sport/action

[slovnitjki]

I have a D70 and I'm looking into buying a decent zoom lens.
I wanna use the lens for sports/action photo since that's what I really wanna learn to take.
As a university student I'm on a budget...and not a big budget so I've started looking towards Sigma lenses.

Sigma 70-200mm f2.8 EX APO IF HSM
This is the one I'm most interested in mostly because of it's good reviews and the 2.8.
If I want more range I could use a x1,4 and almost get a 300/f4.

Sigma APO 100-300mm f4 EX IF HSM
I find this one attractive because of the range. But on the other hand I can almost get the "same" lens with the 70-200 and a converter.

Sigma 50-500mm f4-6.3 EX APO RF HSM
I've also looked a little on this one but the price might be a little over my budget. Although the range is really alluring.

I will be shooting football(the real version not the american ), track & field, skiing, baseball and maybe volleyball and floorball indoors.
So far I think the 70-200mm f2.8 might be the one because of the combination of f2.8 and indoor shooting but I'm a little concerned about the range. I will not use a flash for indoors.

Any suggestions? opinions on the different lenses? experiences?
Maybe you have other suggestion on good lenses.

Cheers..../Magnus, Sweden

[framewerkz]

My partner was shooting with a D70 with the Sigma 70-200 f/1.8 last night at the AC Milan football match. Lighting conditions were challenging to say the least - the match was played in a floodlit stadium. Even from the gallery he was able to cover half of the field, f/2.8 was about the minimum as the shutter speed under those conditions was no better than 1/500. Using a teleconverter will get you further, but at f/4 you're losing too much for the action to be caught properly.

Just for the record I was shooting a Canon D60 with the same lens - 70-200mm f/2.8 - and I had to dump the teleconverter to really get decent freeze of the action.

See for yourself.

http://www.pbase.com/framewerkz/ac