Before you take over the 54-gallon tank, I'm assuming this tank is 48 x 12 x 21" or so high? These dimensions aren't really good for reef tanks with corals because they are so tall and narrow, though they make good FOWLR tanks. As far as the lighting goes, 4 T5s is enough light to grow anything but SPS - you wouldn't need the Radion. The spread of the Radion will only be about 24x24" so it would create a spotlight effect on that tank. Maybe keeping an eye out on the classifieds you could find a good deal on a tank with a better shape - a 24" cube or 24 x 24 x 18" or something would be really awesome with the single Radion!
