Here is what I would get, if you hunt the stuff down, it can be purchased for very little. Best deal I found on Ebay today is this combo. This is the very pump and pumphead I had.
http://cgi.ebay.com/Masterflex-Pump-...item563933957a
http://cgi.ebay.com/Masterflex-77202...item5ad7377948
Basically you want a pump that is variable speed, that can do 6-600 rpms and you want an Easy loader 2 pumphead. Depending on the size of tubing, will determine how much water volume it will pump. Once you figure out that, you are going to be worry free with that part of your CaRx setup.