Check out Elliot Sound:
http://sound.westhost.com/index2.html
I built two 4 channel 60W amps with his designs and printed circuit boards for my tri-amped speakers and they're superb. Even with the shipping from Australia his PCBs are a good deal.
The site has a very active forum where you can get help with building. You can even follow my amp building (mis)adventures there in old threads for enlighenment and amusement. (my username there is just bcoppola)
A little electronic knowledge is needed, though. Nothing sophisticated; just the basics.
There is also a kit maker (AKSA, I think) based in Australia that ships worldwide. I've heard good things about them. Something in the water Down Under?
Now, let me caution you: DIY is fun for it's own sake if you're "that kind of person", but do not be under the illusion that you will save big bucks thereby. In particular, your first project will have a lot of extra costs in the form of tools, equipment, cases, and plain old screw ups. Trust me; that's experience talking! Now, in spite of that I enjoyed building my amps and am glad for the experience and knowledge gained. However, you can buy the Behringer or any number of very good used amps for what you're likely to spend.
Just make sure you know what you're getting in to and why. Things WILL go wrong (maybe not with a kit if you're careful). As Dan Banquer told me, "you're not a member of the club until you blow something up due to a stupid mistake".
I am a member in good standing!
(BIG HINT: When buying components, order extras of EVERYTHING.)
