Alot of people will also point you towards Tunzes. Ff you look at a large return pump, like a Dart Hammerhead. You get under 6000 gph. Two Tunze 6101s get more flow, and use probably 1/4 the electricity (Id have to check).
I initially was going to go CLS also, but was talked out of it. Check with Invincible569, he was CLS, then went Tunzes. He talked me out of going CLS....
If you just want two tunze 6101s, you can get them and a controller for around $700 or so. If you want a Hammerhead and a OM 4way, you will be around $700 also anyhow. Look for some used Tunzes, and you will be happy I think.