Picking out a power supply is not something that should be taken lightly. In a literal sense, weight is one way to determine if a PSU is up to snuff or not, but you also need to factor in how much wattage you need and how it's distributed -- today's systems rely heavily on the +12V rail(s). The easy way to figure out how much power you need so you don't overspend is to use eXtreme Outer Vision's recently updated online PSU calculator.
The handy online tool was updated on Christmas (yesterday) to include a range of new parts, including AMD's Radeon R7 and R9 Series graphics cards. If you spring for the Pro version, you can even select up to half a dozen graphics cards, which might come in handy if you're a virtual coin miner.
Speaking of which, eXtreme Outer Vision added support for a bunch of Bitcoin mining modules. You can select up to five of them in the Pro version.
Other updates include support for Enermax's Liqtech 120X, Liqtech 240, and Liqmax 120S liquid cooling kits, as well as a boatload of processors, including three Core i7 Ivy Bridge-E chips and a Haswell processor.