I think one allure with tubes is that they create a very rich and pleasing sound without alot of tweaking. Sure, you could roll tubes, and do this and that, but you are really 90% there just at the level of the amplifier. On the other hand, solid state takes alot more care and attention to get right. This is because solid state does not create that decay in the midrange that leads to a sense of body, space, layering, texture, and ambiance. However, it IS possible to achieve this with solid state. This has not been easy, but I feel that I am there. I also do not want to deal with the issue of heat from tubes, plus I want that control and extension that solid state provides.
The items below I think all add-up synergistically, and provide the benefits of tube and solid state with little of the trade-offs. Whereas much of the tweaking we do adds detail to the upper frequencies, these items specifically worked on the lower frequency detail:
1) High-quality tube preamp. There are many threads that state you cannot get a tube sound from a tube preamp, but I beg to differ. While adding 2-4 tubes at the pre may not do it, a very robust and quiet tube pre can do things that cables cannot do. For me, the BAT Rex was a no brainer, wanting a balanced connection, 16 tubes total, and with its over-engineered power supply. Others offerings might include ARC, CAT, VAC, or Joule, but I believe ARC is the only one that is balanced in that list.
2) Proper power cords can really add to the bottom-end heft. Elrod Statement cords have filled in the lower portion, which is key to having a full and balanced midrange with weight and bloom.
3) Gold cables add tremendous texture and warmth to the midrange. After listening to Jade Audio cables for 30 seconds, I realized how flawed my Valhalla cables were. I also feel that they give-up nothing on upper and lower extension. The brass can snarl and bite, but it does not have any grain, and maintains its proper place on the soundstage.
4) Tripoint Troy is a grounding system that has significant effects on soundstage width, depth, and instrument spacing. It adds plump and juicing mid-range details.
5) Gold fuses add mid-range transparency, space, and reduce upper treble grain.
The above items are of significant cost, but I feel that each step will get you closer to a rich and full midrange sound. I think both Boulder and Ayre are great amplifiers, and could be satisfying in the long-run with the proper attention.