I've been wanting to buy a set of ND filters for a while now to assist with my seascape photos...

Now i'm thinking of getting a set of the Cokin P series filters, I know this has been discussed many times on one of the other forums i use, and I've asked about it a couple of times... but its come time to bite the bullet...

My main landscape lens is a Sigma 10-20mm F4-5.6 on a Canon 40D... (and eventually in a year or so I'd like to go full frame with a 5DMKII and either the 17-40 or 16-35 so basically the same angle of view)

I was looking at buying a full set of Cokin P series filters, 1,2,3 stop solid ND filters, and 1,2,3 stop grad ND filters and case and all, but then someone suggested going to the Z series so i don't have to worry about vignetting...

Now i'm wondering if i do need a full set or whether there is one or two i could get away with... like maybe the 2 and/or 3 stop nd grad...

The other ND i'm going to get is the B+W 110 10 stop 77mm solid ND screw-on filter...