I ran a 36 by 24 by 21 reef for sometime with 2 2002 and had good success. I will say this Turbelle Classic pumps are great but have numerous drawbacks that have to be seriously considered.
They are high maintenance- these are old fashioned motors with bearings and parts that wear and under ideal conditions last 3 years- unless you have backups for when you have to send them in for service or are yourself mechanically inclined (a rule of thumb is if you are capable of basic auto care like oil/ air filter and spark plug changes you can likely handle it) If I do it it is usually about $25 in parts and $15 in labor.
They primarily circulate the top end of the aquarium and are not ideal for deep aquariums. The pump itself is 1" below the water line and cannot be submerged deeper without damaging the pump. In aquariums deeper than 24" I find they are not sufficient flow in the deeper reaches.
They are expensive to control. Control of the classic turbelles requires a multicontroller outfitted with special sockets which vary the power to the pump- a control kit is about $260.
They make noise from a cooling fan- they sound like a fairly noisy PC cooling fan- if I had to quantify it it would be 30db.
With that said the Classics are probably the only pump in the world that will absolutely last forever- they are almost infinetly rebuildable and have some great features, the flow can be dropped almost to 0gph, they are electrically waterproof if they fall in but of course the mechanical components would be ruined (bearings and seals and spacers). They also are nearly invisible and add no heat. Myself, I am sick of rebuilding them, I own 12 and I see at least 1 per week from somewhere in the US/Canada or Mexico needing to be rebuilt, it takes about 15 minutes but can be a pain in the arse. I would buy a 7400/2 or 2 7200/2 and a controller and just accept that you will have very beautiful German made pumps to show off to people- frankly I wouldn't mind having an engine in my living room as long as it went to a Mercedes Benz.