Wow, I really appreciate all the advice.
Speakers and room treatments are high on my list of future upgrades. When I started this thread I was also hoping for some more general "philosophical advice" about making the jump from mid-level to high-end audio.
In that spirit, I think the posts so far suggest the following more general advice:
1. recognize up front that the improvements you make with larger investments may be smaller and more incremental than you expect,
2. be sure to optimize your current system before making changes, for example, with speaker placement,
3. know exactly what you want to improve with future upgrades,
4. hear as many systems as you can, for example, at a national audio show, and
5. build your system around the speakers.
All of your advice definitely resonates with me. I'd love to hear some additional perspectives from others who've gone down this path before me, though.
thanks again.
e