Suggestion used tube amp between $1,500-2,000

For $2k, you can pick up a used Music Reference RM-200 (the original, not the Mk.2). It is well-suited for passive pre-amp use (input sensitivity, gain), so you can dispense with the LS-7 and get a better-sounding passive if you wish. Over twice the power of the good Quicksilver suggestion from yogiboy---100w at 8 ohms from only a pair of KT-88's per channel. And unlike any other tube amp with which I am familiar, more power into 4 ohms! 

The input impedance of the RM-200 is 30k via it's XLR inputs, I believe.

Ah yes Al, unbalanced only on the LS7. Of course, if Eddy goes passive, he could get a passive pre with balanced out. They are available, aren't they? Not that Eddy indicated any dissatisfaction with his LS7, but when I see a system with a single line level source, I think passive pre. Roger recommends that route with the RM-200. An even better course of action, if the source allows it, is to install an attenuator right in the source component. No impedance match to worry about, and one less interconnect! Ric Schultz of EVS used to make a great attenuator, of discrete resistor-ladder design. VERY transparent.