The types of coral and critters you want to keep is what determines the type of lighting you need. If you like frogspawn, torch, and mushrooms, then you don't need much light. If you want anemones, clams, and SPS, then you need lots of light. 28w is low for a 10g tank, which means you can do shrooms, softies, some LPS. I've got 32w over my 6 and I have a ton of stuff, and it's very colorful. So it just depends on what you want to keep. I've got a 96w coralife fixture over the 10g that I just took over from my wife. I'll be able to keep more in that tank once I get it under control. There isnt' any reason to spend a bunch of money upgrading your lights through the roof if what you want to keep doesn't require high lighting.
B