as an aside, the position of yer preamps' wolume pot may not be indicitave of anyting, other than the gain of the preamp. i've *never* had my preamp past 11:00 for winyl, never past 10:30 for digital or tuna - i'd be blown outta the room! and, my room is ~25x38. my preamp has lotsa gain - supposedly enuff to drive many speakers w/*no* amps at all... ;~)
re: your situation, john meyer of newform, sez the r645's are better w/an outboard active x-over, bypassing the passive x-over. if it were me, i'd get a pair of the stratos stereo amps w/the upgraded caps, & run 'em in a wertically-biamped mode.
i actually *almost* bought this exact set-up from klaus cuz i was looking w/o success for an electrocompaniet aw75 to match the one i owned, so i could run these in this exact fashion, (*or* run 'em mono, as they can run either way.) yust before i took the plunge, however, i found a great deal on a pair of aw60's, so i got them instead, as i already knew & liked the electro amps. different amps, but exact same idea. i have great results running my bi-ampable speakers w/the electrocompaniet amps, wertically bi-amped.
while ewe won't get *all* of the power benefit of the mono's - the total power w/mono's is awailable to *any* driver - yule still have more power than running yust the one stereo amp, & yule still have a complete separate amp for each channel. plus, ewe get the added benefit of being able to have a true bi-amped set-up, w/one channel for the low-pass, the other channel for the hi-pass. i'd do this w/any bi-ampable speaker, but w/the r645's being able to use active x-overs, there's even *more* added benefit, imho. of course, if ewe can afford *four* stratos monoblocs... ;~)
good luck, doug s.
ps - i'd like to hear your reaction to the newforms - i'm strongly considering taking the plunge...