There are 3 power supplies shown here. I use the 20amp, single outlet. I made my own distribution box so I can run two chargers from it at once.

http://www.hobbypeople.net/mfr/propek01.asp

There is some inefficiency/loss in any charger, if you need to charge at 5amps, you power supply needs to be rated for more than 5amps.

There are a lot of power supplies out there, for something real cheap if you don't mind int'l shipping, check out HobbyCity's site. Their 5amp supply (laptop power supply) is rated 5a, but has been tested at 6+a. Its about $10 IIRC.