I've also built a couple PSU-based power supplies - and they work great. If you're clever, you can get them packaged up quite tidily as well.
However, next time I'd just go for one of these and be done with it.
http://www.ebay.co.uk/itm/Dell-Power...item35b46281ad
No fuss, no muss. You do have to rewire the output cord to something more useful, but a quick google will set you straight.
Cheers,
Ty