There will be alot of different ideas about that question and alot of it will be determined on what you want in the tank....corals etc.
I placed a couple of Penguin 550's in mine. Place them so that they are running counter-current and aggitating the water surface to increase gas exchange...just an idea.....
Place one on the left angled right and up
Place one on the right angled left and down
Corals and anemones require different levels of current. If you decide to buy any of them...read up on them to find out what kind of current they require and make the adjustments.
Marine Fanatic hit the nail on the head. But I would not purchase penguin powerheads, though. Go with MaxiJets. They will cost you a little more, but definitely worth it. HTH
I 2nd the maxijets. they have ALWAYS worked for me, i won't waste my $$$ on anything else. They won't add any heat to ypur system and don't seem to jam up. I run 1-900 & 1-600 in my 45g, along w/ my penguin 330 hang on filter. HTH
maxi or aquaclear is all i buy and
position them, so the currents cross, not so they whirl pool in the tank, i myself would use 3 smaller ones minimum, instead of one or 2 large powerheads
HTH
i have 46gal bowfront as well. I have two aquaclear powerheads 402. i have one in the middle of the tank which bounces off the front glass and dispurses to both sides due to the curve in the glass. the second one is on the right of my tank. it is turned on an angle left to bounce off the front of the glass as well. It is on a slight angle facing upwards. The two clash on the middle to right side of my tank making nice current. top water looks like they are going crazy.
Oh yeah you can modify your aqua clear 402 to become faster as well. You saw off the bottom where the controls are. They go crazy this way. Ask you LFS I dont want to see you waste money and cut it wrong