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?

How funny, I'm actually building the same preamp with the same LM chip,

I've only tested it on an oscilloscoop and it seems to work,
just waiting for my LM chip that i've ordered, then I can fit it in my case,
I cant wait until I hear the sound coming out of it,

Has anyone build it by now?

I'm also curious what I have to do, to supply it with a +/- 20V ?