Hi - It appears that no one responded to your question a few months back about the SE9's, and it also appears that they were once popular on this forum (a few years back) but not much mentioned anymore, so I thought I'd put my two cents in and see if anyone out there has tried the larger, more powerful SE18.
We purchased the nOrh SE9 several years ago and have used it happily with a set-up consisting of Linn components (with the exception of a Mark Levinson pre-amp). The SE9 is a wondrous little amp -- I'd recommend reading the excellent, thorough review posted at http://www.tnt-audio.com/ampli/norh_se9_e.html -- and we've been very happy with it. For even twice the price, there is nothing that compares. We listen mostly to classical and jazz, but some contemporary as well (e.g., Dave Matthews) and the warmth of the tube does great things for vocals and making instruments sound organic and musical. The SE9's are outstanding with headphones, too.
As you might expect, however, they don't work well with inefficient speakers. We tried them with the Manger Zerobox speakers (which are a musical revelation in themselves, but quite inefficient), but they blew the tubes after a few hours of testing.
Note: we upgraded the tubes with Russian NOSs, which improved things further.