Preamp Suggestions with LFE output

I have an old Audio Research LS3 with two sets of outputs.  If I drive my sub with one and the other drives my Threshold S/200, the S/200 is way more sensitive than any sub I have tried.  The only way I was able to use the sub is to put a couple of RCA 6DB pads in the input to the Threshold.  while it balances out the sub nice it kills my highs.
I really want to move to a preamp with LFE outs with a level adjust for that output.  TI can go with a number of surround processors, but it is a dedicated listening room and that a whole lot of crap I dont need.  I guess I could switch to an amp with a level adjust on the inputs but havent seen any of those in this world.