Tboooe,
How much did you decrease the input gain or as BAT calls it "Relative Volume" adjustment? Try setting it lower. If that is properly set, you should be able to use the main volume knob in a wider range. A CDP with 1.7V output is not high at all, so if even using a player with that output should not overload your preamp. Also make sure, you don't have the Fixed Gain mode "On" for the BAT preamp, cause that might bypass your input gain adjustment (I'm guessing???). If your Classe has 14 gain, and the BAT is 17 gain, that's really close. The Classe can go +/- 14 ticks of gain, so I am assuming the BAT can go +/-17 ticks of gain. So you should be able to lower the BAT to sound like the Classe in terms of gain input. Just go as low as you can, and slowly inch your way up on the BAT input gain. I think you should be able find the right setting after trial and error. If that doesn't work, something seems wrong with the BAT preamp then.
Good luck.