I am just getting parts for mine put together as well, I just ordered a 2 diffuser set and weighted air tube, I am buying different air line from lowes to bury out to the pond, I will probably buy a thomas 2660 pump off ebay, they have several on there for around $75. All together I might have around 450 in the system. PM me if you want more info, My pond is around 3/4 acre.
