They do sound great through a PA or speakers. When I use mine I play directly through my computer so I can get the cleanest sound possible for the GT8. When you get the clean sound (PA or Computer) you can get really nice sounding tones from classical to metal.
From what I have heard GT8 has better clean tones than the POD XT Live and the POD XTL has better heavy tones. But GT8 has satisfied me in both categories so I'm not complaining.
Really to make it worth it, read the manual and learn about it. That way you can make the best tones and patches. If you don't like it most stores such as Guitar Center will let you return it for 30 day satisfaction guarantee.
Hope this helps you make your decision. Any other questions please ask.
"If you have control over your mind, you can do anything"