First, DO take notice about putting steel strings on a classical guitar!!! It will soon be wrecked if you do it!!! I play a little blues but mostly folk - however, please read on. I used to use steel, then Spanish nylon strung before going back to steel-strung folk. I now play a Lowden. I know you said you were less concerned with brands, but I chose the Lowden (it is model 025) because it is, for me, a fantastic combination of the best of 'folk' guitars and the best of Spanish. It projects wonderfully, has a beautiful rich, deep, fat tone, and a wider than usual fretboard. People have often commented to me on its classical-type tonal qualities while retaining the punchiness of a steel-strung. It all depends how you play it, and it responds very sensitively to the way it is played. f you don't know whether to choose nylon or steel, try Lowden - it will give you the best of both worlds. There may be only one problem: you said you want second-hand. Second-hand Lowdens are difficult to come by. Once you have bought one, you will not want to let it go!