It's not smart to use voltage regulators for your poweramp, it can't give you all the power needed for your poweramp,
just build a supply like this (scroll down to "power supply")
http://sound.westhost.com/project27.htm
make sure you have a proper transformer, probably something about 80VA,
the voltage coming from your supply depends on how much voltage you get from your transformer,
if you buy a 2x25V transformer, you'll get a +/-35V to supply your poweramp,
the 18Volt you have read on the datasheet is the minimum voltage it needs te work properly,
so if you use a larger voltage, it's ok, I will even give you more power
just curious which preamp you will build for it?
just build a supply like this (scroll down to "power supply")
http://sound.westhost.com/project27.htm
make sure you have a proper transformer, probably something about 80VA,
the voltage coming from your supply depends on how much voltage you get from your transformer,
if you buy a 2x25V transformer, you'll get a +/-35V to supply your poweramp,
the 18Volt you have read on the datasheet is the minimum voltage it needs te work properly,
so if you use a larger voltage, it's ok, I will even give you more power
just curious which preamp you will build for it?