I wouldn't get to bummed about your Koralia 2's. The Koralia series is unique in that it does not push water in a "jet" like motion, i.e., one concentrated stream. Yes you will feel the push from a Max-Jet farther away, but it is pushing all in one place. The Koralia series of heads typically move more water than a power head of similar size, with the huge exception that they distribute the water flow evenly in all directions. I have one Koralia 1 and two power-sweep heads in my 70 gal. I just ordered 2 more Koralia 1's to replace the sweepers for 2 reasons. First the Koralia's take up less room and are far more appealing to the eye, if you have to look at a powerhead in a reef tank, and 2, they put out more flow than the sweepers do. 3 x Koralia 1's = 1200 gph plus about 350gph from my canister filter return moves roughly 1500gph, give or take, through 70 gallons. Thats about 21x turnover per hour. Just 2x Koralia 2's in 46 gal is about 26x turnover. Even if you place the heads in oppostie corners, there should be enough flow to produce enough chaos in the current for you to have a great reef atmosphere.
However, I am no expert on flow. Just personal experience and opinion. I'm sure that there are those who would argue with me, just like any other piece of equipment can spark a dispute. Hope it works out for you, good luck!
