I've used Whisper, AquaClear, and MarineLand (Emperor and Penguin line) hang-on-back filters, and Fluval in-tank filters, and been satisfied with them. I don't really like Duettos, as I've had problems with them failing after a couple of months. There are a lot of other brands, of course, and hopefully someone who has had experience with them will pipe up.

Direct sunlight isn't bad for your turtle unless it severely overheats the tank, but it can cause algae problems.