I have a GK 410 cab w/ Eminence spkrs. and a Hartke 3500. I'd like to add a used SWR Big Ben 18" to it. I'm wondering if they'll compliment each other's tone and can they be stacked? I may not be thinking clearly, but the specs seem like they won't fit - GK410 - 23"W x 27.5"H x 18"D Big Ben - 23"W x 30.5"H x 18.5"D Any thoughts?