I think the non sloping top tube might be the deal breaker in your criteria...............Marin and Kona made some nice steel frames in the early 90s but I believe they had sloping top tubes. Should be easy enough to find a good steel frame as everyone seems to be abandoning their 26" rim brake'd rigs for disc's and 29ers. Dependant on how aggressive you plan to ride off road, a CX frame might be an option.