I have the Xt Live and it requires tweaking to sound right live VS recording or headphones. I have used it through my little 25 watt tube amp and the same setting is a bit different through the headphones. However, the sound in the headphones and the sound through my 100w power amp and a set of monitors is very close.

So bottom line you will need to tweak when playing through an amp or you can just use the pa system. I have heard the Atomic amps are made specifically for amp modelers and the bean fits into the amp. I have never heard or used one so I can't give you any specifics.

As for getting good tones through the POD Tweak,Tweak,Tweak..... And use the EQ to clean up the sound. I find the pods distortion is to distorted for my taste (muddy) but I can usually clean it up with the EQ.

Hope that's of some help.