Jc: I'm generally in Czarivey's pew on this one, particularly for classic rock records from the 60's and 70's. The original pressings often sound far more lively than the remasters; yes, you have to deal with 'condition,' but as you obviously know, buying new vinyl is no guarantee of pressing quality (leaving aside sonics).
I bought approximately 1,000 records in 2013, most of them used. Happy to provide sources, but often, the issue isn't the dealer, but knowing what pressing to buy. I highly recommend that you dig in to places like the Steve Hoffman forum, which is an enormous resource for rock records of this vintage; you'll see multiple threads with comparisons of various pressings, not all of which are expensive. (In fact, there was a thread comparing sonics of the remaster of Brother in Arms (the two record version) to various earlier pressings.
If I'm buying new pressings, I usually try to buy directly from the source, e.g. if it is Analog Productions, from Acoustic Sounds; from MoFi, directly from MoFi or Music Direct (which now owns MoFi), Music Matters for the Blue Note reissues, etc.
FWIW, I've had very few bad experiences buying used records over the years. New- mixed bag on quality. One of the benefits of 'used' is that many sellers will play grade (visual grading is pretty useless) ; a sealed record, old or new, is a riskier proposition.
Also don't know if you own a good record cleaning machine, but I consider that to be essential, whether the records are new or used. Along with a stock of high quality inner sleeves, to replace the paper or plastic sleeves that often come with new reissues (MoFi, Acoustic Sounds, etc. tend to use high quality inner sleeves; some of the 'standard issue' remasters from major labels, less so).