Cokin filters for my D80

[herc182]

Dear all,

I have the kit lens 18-70mm and the sigma 10-20. Because of the latter and a gander on the Cokin page:
http://www.cokin.com/ico15-A.html

I would need the cokin x pro. I am thinking that i could get the p series and remove any vignetting with capture nx.

Two questions:

1 - do you think this is a good idea?
2 - will there actually be that much vignetting if i got the p series? maybe get the z pro?

Its a lot of money!

Any examples of photos taken with COkin appreciated. Website to buy from also (in the uk).

thanks in advance!