I swear by the D5's, like everyone else has said. They just simply work. If you're on space constraints, XSPC makes a D5/reservior combo right
here.
While I like the MCP35X for it's pumping power, sometimes it's hard to fit that neatly into a cooling setup somewhere in the case. That's just my opinion, however you can buy res attachments for it that look pretty sweet.
If you're on a tight tight budget, go for a Danger Den CPX-Pro. Little louder of a pump (slight buzz coming from mine), but it gets the job done.