Are they rated at 600 gph, or is that the actual flow that you've measured? If you're really pumping 1,200 gph with the two of them the fish must be working pretty hard to stay in one place. The largest canister filter that Eheim makes in the classic line is the 2260. It is rated at roughly 600 gph, but that's with no media, piping, strainers, spraybars or anything. In actual use, flow is probably 1/2 that. It's a beast and holds almost 5 gallons of water itself. It is "sized" for a tank of up to 400 gallons.
An Eheim Pro III is rated at about 450 gph and Eheim lists it for aquariums up to 320 gallons. Obviously, you can see that I'm biased toward Eheim, but there are many others out there that work perfectly well. I'm planning on two 2217 classics, each rated at about 260 gph and sized (per Eheim) for up to a 160g tank. I don't really buy into Eheim's ratings so I'd plan on at least doubling or tripling what they recommend. IMO, they do a much better job of filtration than circulation. This is why I went with a separate Eheim 1260 in-line pump to run the CO2 reactor, UV unit, and 66" long spraybar.
I suggest starting a new thread in the "Equipment" section where more people will see it. I'm sure you'll get lots of opinions. Just remember that Eheim's actually are the best
