I haven't heard this combo, but I own an Stereo 90 (being upgraded to Super Magnum at Rogue as we speak).
In general, bass is usually considered a strong point of Rogue amps, compared to other tube designs. And the Magnum versions and KT120s should both enhance that bass performance. Bass performance was certainly one of the factors that led me to choose Rogue over other tube options around the same price.