There's something called the, "Fletcher-Munson Effect" that defines how one's hearing response varies with acoustic(DB)level. As in: Less sensitive to lows and highs at lower volume levels. That's why some equipment(usually mid-fi) will be found with a, "loudness contour" of some kind. You didn't give much info to go on, with regard to your system. I was using a Placette Passive Linestage, between my Cary SLM-100s and BAT VK-D5 for awhile. The transparency/musicality was wonderful at all volume levels. The passive shouldn't be depriving you of anything. It's probably that the B&Ws aren't the most efficient speakers out there, and don't, "wake up" at low power levels. Planars are usually mid-efficient systems as well(86db/1W/1M, or thereabouts, in general) and (as much as I love them, having owned Acoustat Mod IIIs, and a few Maggies) probably wouldn't avail you much at lower levels. Audition some higher efficiency speakers(90db/1W/1M or better)at low listening levels. There are some fairly efficient systems out there with ribbon-type tweeters. The option is finding a pre that induces no personality of it's own, and yet offers some bass/treble boost at lower listening levels(good luck).