Do a little forum reseach... our guys like J J have posted in some detail about how to buy the necessary blocks, fittings and valves from places like the Surplus Center to do it own your own. There have been some threads on doing just that.
I just got some fittings and hoses from the Surplus guys, and spoke with a man there who seemed to have a LOT of knowledge about hydraulics. I think working with what's on this forum, and someone like the guy I mentioned, you could do it without much worry and at a reasonable total cost. The kits are nice, but there's nothing magic about them. Sure is nice to have the extra circuit(s) when you need them.