A used Plinius intergraded (option of using as an amp, preamp or both) 8100, 8150 or 9200, will easily drive the 1.6's with plenty of volume and sound some what tube-like. You should be able to find some on the used market in your price range.
A used Krell intergraded is also a possibility, but I'm not sure of the pricing?
A used Krell intergraded is also a possibility, but I'm not sure of the pricing?