Well if was me and I was going DIY (which I probably would never bother with again) I'd go with the LEDgroupbuy heat sink
http://www.ledgroupbuy.com/makersled...ssional-grade/
Maybe I'm missing something but the aquastyle heat sinks are pretty standard, nothing sleek about them really. By the time you strap on a fan and splash shield it'll look pretty ghetto.
For LEDs I'd probably attempt the 3-ups, ideally ones with 1 RB, 1B & 1NW, all Cree's or Luxeon's (around the same price). For a 20 gallon I'd just wire all them together and do a simple on-off with a single ballast, keep it simple. I wouldn't bother with any other colors except maybe violets. On a small tank it's pretty hard to get good color blending, especially with DIY, don't think it would be worth while.