I own two preamps and one linestage and I cannot really decide which is the "best" among the three, never mind the whole universe of products. Each has its strengths and weaknesses.
The most detailed, dynamic and extended in frequency response is the Emotive Audio Epifania (linestage), the one with the most musically seductive midrange (but with less control in the bass and less extension on top) is a custom built preamp using Western Electric input and output transformers, and easily the least sonically appealing is a Levinson Ref. No. 32 preamp (but I love the convenience features and incredible flexibility).
I have not heard that many other contenders in my own system, but, I've heard many other great systems built around such linestages as the Atmasphere linestage, the Veloce linestage (can be configured as a preamp), the Audionote (uk) M-8 and M-10, the Kondo M-10, Burmester linestage, and a Shindo linestage. I can't say whether any of these are a "contender" because I haven't come close to hearing but a fraction of all linestages, and I am certain that quite a few that were in systems that did not impress me were not at fault. A number of great linestages I've heard were custom-built (essentially one-of-a kind, and not widely available).