Need more bass response

Your complaint and, shall we say, skepticism are well founded. I think you have all the right feedback, so let me try and simplify it. Rock recordings are typically mastered differently than jazz or classical. They tend to be compressed (remember AM radio) and not very dynamic. CDs are not all created equal. Car stereos, no matter how expensive or what brand, need to compensate for road noise; hence, bright and boomy. And, you do have tone controls in the car. But, I still would not use it as a comparison. A square room is an interesting animal. Play with placement and possibly even relocating a piece or two of upholstered furniture. Hey, become an acoustical designer for the day. Maybe you need two speaker locations -- one for listen and one off to the side for when you are not listening. Moving them is a pain, but may be the answer. Your equipment is fine. Belles has always made nice amps, but it may be mismatched with the Rouge or, dare I say, your cables. Reconsider your tubes. Have you tried the amp with a passive device instead of your Rouge? I am not saying dump either but rather isolate some of the equipment to help diagnose the situation. I left the best for last. Wires do make a difference, but you do not need to mortgage your grandchildren. I used a very nice and affordable wire from Sweden. DH Labs and Mapleshade have good product, as do 25 others. The DIY Belden wires give good sound. Stan Warren's daughter makes some killer cables and very affordable. So, as much as you may want to avoid this journey, it is worth the effort. If you have a good relationship with a dealer or two, go back and ask what they have floating around that they do not use (sell) anymore or even just start borrowing. You have reached the point where you can make a mistake out of frustration. Take it a little at a time and have patience.