FWIW, I'm solving this problem by using a NuForce AVP-16 as my pre-amp, which drives a Parasound HCA-1000 2-channel amp. So, basically, I am using a surround-capable pre-pro as a 2 channel preamp. It works pretty well - the NuForce has a repuation of having good SQ for music (and this combo, with my Onix Ref1 monitors sounds great to my ears although I don't have much to compare it to). I'm able to use the NuForce's bass management to cross the mains over at whatever frequency I like.
So, no, this does not solve your problem of wanting to do this with an integrated. But the NuForce/Parasound combo cost me about $1k off Audiogon. I'm not sure I would have gone this way had I set out to do purely 2 channel to start with - I originally had hoped to do surround music, but have since changed my mind - but I am actually quite happy with the result. I probably won't switch over to a "pure" 2 channel pre until I get speakers that go deep enough such that I don't want a subwoofer anymore.