Sounds to me as though you've done your due diligence on getting a sound you can live with out of your Rumble. I wouldn't waste any more time on it. In my opinion, any solution other than "D" is just putting off the inevitable. Regarding trying things out in a store, that never told me much. When I was gigging full-time, the only way I could know for sure that something was going to work for me was to take it on stage with the band on the gig. Back then at least, that wasn't an option with an amp rig. Because of this, I looked at what the greats were gigging with. I went with an SWR Redhead because Marcus Miller was using it and a friend told me that when he was in NYC at Sadowsky buying his bass that's what they had him playing through. So, "If it's good enough for Marcus and Sadowsky..." I ordered one from Bass Northwest (I miss those guys) and it was great for me. With all due respect to the Fender Rumble line, are there any "greats" that endorse them and actually use them live?