Get the GK over the SWR. 480 watts out of this head will crush the SWR. Definitely use two cabs and get the full output. Regardless, the Aural Enhancer and Contour knobs do the same thing tonally - cut your midrange while boosting highs and lows. If you want to be heard amongst your bandmates, make sure you turn both of those knobs all the way to the left - off! Is the rig for a stage monitor or for your audience?
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I don't know how SWR stays around the market these days. The tone out of almost every head I have tried has been weak and boring. They may have beautiful clean highs and what not, but unless you are in a quiet band or a soloist, these amps should be chucked into the trash. This opinion comes from a rock guy, so to all of you SWR people that love these things - I am sorry! Please keep rocking them. But honestly, you can get growl out of the GK head along with plenty of midrange punch coupled with solid low end - you will be heard in your band. Last time I saw a SWR rig (in nearly the same situation as you are in, but without PA support) he was blasting a 550X, 210 and 15, with that Aural Enhancer at noon. I could not hear a damn thing he did unless he was soloed.