Ya, the active air HSF now a days are pretty good. I'm not nearly knowledgeable about water cooling so maybe this might be a bias opipion. But here's my logic on water cooling vs air cooling. Water cooling first and formost is very expensive. The parts listed above are $200+. I can get a top of the line air HSF for ~$80. Yes there would be a preformance in cooling with a water block but it might not be as much as you'd think. Another thing is that water blocks can leak. and if they leak...well you know what happens when elecrtical parts take a dip in water. With air you don't have to really worry about it.
The only reason why i'd say go for a water block is if your doing it for cosmedic reasons. You want your case and stuff to look cool. For me this isn't a big concern but for many people that come here it is, so i understand if that's the case. Girls love it when you can tell them you've got a big block.
If your going for world class overclocks then i'd be looking into phase cooling and not water cooling.
Here are some very impressive air HSF that i'd recommend, and save yourself at least $150.
Noctua se1366 - One noted above
coolmaster v8
coolmaster v10 - this is overkill
Dark Knight - will also need to get the back plate for this.
TRUE - Will also need a backplate with this guy as well.