Laura, we now know a good deal about your system. But I did not see any details on your room and setup. The amp problem is just that, an amp problem. You can get a new or used amp from many well known companies and not have to worry about the issues you have right now. Two channels would like do it, as the 3808 can clearly run the other channels. Open any audio website and the trusted names will be published and reviewed often - e.g., Parasound, Krell, Bryston, McIntosh.
But I'm struck by the fact you have the 3808 as a pre-pro. You are nearing the price of separates, and have separates, yet you have a wasted amp section in the 3808 and a sub-par pre-pro for the price. Why didn't you want a dedicated pre-pro? Just curious.
Given the general confidence that people have in the 3808's amp section, and the size of your room, I'm thinking you could use some time/money on speaker placement and room treatments. You are clearly willing to pay to get good sound, but no amp or tube will fix the first order reflections blurring your image, or the modes of your room causing muddy bass, etc. (It will fix loud, which I like!) Have you plotted the frequency response of your room? If not, try that. If/Once you have that data, you will find lots of advice here about how to improve your room to get the most out of what you have - which is plenty for an audiophile system, with or without a separate amp.
