I use and A. E. Tech skimmer and sump on my 125 gal reef. It's a larger version of what you are looking at. I find their products to be of excellent quality and can highly recommend them.
If you go with them, I'd go up one sump size. It's only $30 more, and I believe it would still fit in your stand, but check! The larger sump gives you more water volume,
One thing you'll notice about A. E. Tech is that the don't offer overflows. You'll need some sort of overflow for your tank. Ideally this should be an internal overflow, but that requires drilling the tank. Many 55 gal tanks are made of tempered glass and can not be drilled. The alternative is an external overflow. The best one of these I have found is made by Lifereef. See them here -
http://www.lifereef.com/home.html I use a Lifereef overflow on my 125 gal reef, because that tank can't be drilled.
Lifereef also makes sumps and skimmers so take a look at them also. They also make an excellent product.
Can you find a better price? Well, maybe, but usually you have to give up something. If it costs a lot less, it's going to be of lower quality. Corners were cut some place. Acrylic plastic sheet and tubes are expensive, and that usually translates into expensive equipment.
Some people also build heir own sump. They use a tank similar in size to the sump they want and add the necessary baffles and other things. This is a good way to save if you are into DIY projects.