I purchased new a SP9MkIII in 1996, just after manufacture was ceased, and found it utterly reliable - it was in my system until last year. At the time it was compared with the MkII and it was markedly better, especially in regard the phono stage; also the LS7 which, from what I remember, was good but not quite as open and, if anything, more analytic despite having a larger complement of tubes - the store staff seemed to have a soft spot for the MkIII, to the point where, on a visit to Sydney by Bill Johnson in 1997, one asked him whether any were tucked away in the factory, and he offered to construct one from spare parts, which ARC did in fact do! The reviews, professional and informal, seem to favour the MkIII too. I think it should be in your budget. If you listen to vinyl, it really is tremendous.
I'm sorry but I haven't listened to the LS 1 through 3s. The more recent ones, such as the LS25, sound great, but cost far more. The only one which I would avoid is the LS22, which even the store staff could not recommend.
As far as SS amps the only one I've tried, and that briefly, was an old Gryphon S100 - terrific, but rare, expensive, only balanced inputs, and not necessarily reliable.