Chaz, something to think about is which size cokin filters to use, A or P or be really adventurerous and go for Z. The P size is probably the better option if you are thinking of carrying on with landscape for any length of time. AP did a review of filter systems a few weeks ago, so it may be worth checking out their web site for some hints and good advice.
www.amateurphotographer.co.uk. For some reason i cant put a link in, sorry.
Are you sure your second filter dia is 56, and not 58mm.
Dean.