Serious Passive Preamp question

I am a huge fan of passive preamps but in this case I feel you would be best served not to make that trade, and I am not a big fan of Audio Research equipment. I am assuming by the price you mentioned that this is the Serious Stereo series type model (not the ladder type), but regardless both are pretty far down my list of passive preamps that I have listened to over the years. I would say based on a cursory look at the specs for your amp a passive preamp would match up nicely (you do have to consider the source in the equation as well) and you should consider trying one, just not  this one.

I went passive recently, but held on to my preamp until I was sure I was happy with the passive. Passive is not for everybody. IMO, I do not think it wise to do the trade. Enjoy ! MrD.

For a passive, I don't think that would be worth anywhere near $2200.  It's just a couple of stepped attenuators using larger "through hole" resistors.  It doesn't even have anything special, such as signal transformers like other exotic passive preamps.  Definitely not worth a trade for a LS7 linestage - you're, essentially, getting screwed on this trade if you do it.
If you really want to see what a passive does, try a Gold Point SA4 ($532), or an SA2X-I if you want balanced XLR passive ($616).   If you really want to go on the cheap, Shiit SYS for $49.