It may be sacrilege to bring it up but if you want to ride on both roads and trails a ss may not be the best choice. You will at least need a flip-flop so make sure whatever frame you get has canti-mounts. Is flipping a wheel whenever you switch from road to trail worth whatever benefit you see in ss. If so I would get a qr on the back and avoid ebbs in favor of track ends to make it as little a hassle as possible. Also remember that you tire will be on backwards one way.

Be very very careul with steel. Ultra light steel frames are a durability nightmare. The alloys and treatments used make it about as brittle as Al and in conjuction with the paper thin walls this means even a low speed crash can trash the frame.

I agree with all the people suggesting cx frames. Unless you want to ride technical single track it's probably the best option for you. In your price range you could easily afford a custom one with track ends if you are set on ss or you could get a multispeed one and make a 9-speed.