I have Bottlehead Monamour mono blocks driving Altec Model 19 clones. I use a Schiit Lokius: a 6 band equalizer. Adjustments at 20, 120, 400, 2Km, 6k and 16K. $300. I have also used the Loki Mini Plus, 4 bands, $150. These are unbelievably transparent and effective. I recommend them highly. And, you get a 15 day trial.