I run one. Aqua Ultra Violet. I like it a lot. No, you will need to spend more to get one that is worth while.
A UV sterilizer is most effective when you pass all the water through it, between the sump and tank. This means that you have to have one that can kill protozoans with a single pass at whatever GPH you run from the sump to the tank. When I bought mine, that meant about 1000gph flow, so, 57W! Now, my sump is flowing about 1/2 that, 500gph or so, but I still use the same 57W as I already have it.
If you get a small one, and pump water from the sump into the UV, and then it goes back into the sump, your UV will be far less effective.