I have the Canon 50D
I am going to buy the Sigma 70-200mm f/2.8 EX DG OS HSM
I believe a great all round lens even in low light.
along with either the Sigma 1.4 x or the 2 x teleconverter

I mainly shoot Rugby league (mainly from 2:00 pm and later) Nice and close to the action.
Want to try my hand at surf photgraphy.
Do I buy the 1.4x with the 280mm reach @ f 4 or go for the 2x with the 400 reach @ f 5.6 .
Would I loose to much quality with the 2x.