I've heard a few of the contenders, some in systems I am familiar with, others in somewhat alien systems. One of the best systems I heard had the Audionote (uk) M-10 linestage and phono stage. But, that is a huge and extremely costly setup (well over $100,000). Of course I would have purchased it (NOT!) if it came with a remote control.
My other favorite is another tube-based linestage, the Emotive Audio Epifania. I've placed an order for one with the premium teflon capacitor upgrade (I auditioned a model without the teflon capacitors for two weeks) and remotely controlled volume and input switching. On good recordings, the sense of a performance in a real hall, with notes blooming and then decaying in space naturally, is absolutely amazing with this linestage. It makes my current ML Ref. No. 32 sound so artificial and mechanical, by comparison.
I've also heard nice sounding systems with the NAIM 552 linestage. I know this sounds odd, because it sounds so different from the Audionote and Emotive Audio gear, but judged on its own terms -- emphasis on detail, dynamics and precision, this is a very special linestage that manages to have all those qualities and still sound musical, relaxed and satisfying (it lacks some of that magical "bloom and huge image scale of top tube gear).
I've heard the Connoisseur and the Boulder linestages and phono stages, but not in systems I am completely familiar with, so I cannot comment on the sound. Both are very pretty to look at though. The Boulder is also, like my Levinson, extremely versatile -- an amazing array of adjustments can be made by a very logically worked out remote control.
