Here is my input on a few of these topics.
1) I agree that audio is a personal preference but it would not have cost much more for a lager TV instead of the side cabinets. Besides other RV companies install more complete audio solutions (not necessarily high end) that have larger TVs, surround sound instead of sound bar, a subwoofer.
2) Grand Design should reconsider their audio components to be more in line with their upgraded features such as the plush theater style seating, huge pantry, kitchen Island, large bathroom, decor, etc. Also, the Solitude is sold as "extended living" so we want a nicer audio experience when we re enjoying relaxing time when we spend 5 months in the RV every winter. Its not "camping", its living in our cottage on wheels.
I upgraded our "RV theater system" with a nice LG BH7520 3D Blu-Ray HTS on clearance for only $100. I replaced the false wall behind the TV with a new back board that opens up like the cupboard door above the microwave so I can use the space behind for my printer and other items. The only difficulty was the huge Sub-woofe which I will install behind the fireplace (came with smaller speakers than original ones that worked to my favour to install in RV).
Thanks to Andy for his info on his subwoofer install behind the fireplace.