Bi-amping Snell Speakers Anyone?

it sounds to me that while your amps are the same, they may not be matched for some reason. Did you connect in vertical or horizontal config? If Horizontal (ie one amp driving mid/tweet, the other driving bass), try vertical. If one side is louder then your amps output aren't matched.

My experience is that passive biamping does produce an improvement, but it is not huge relative to the cost of buying another amp.

I've had similar experience. I've tried many amp combinations on 2 separate systems and found one case where biamping produced improvements over one amp material enough (to my ears) to keep it running in biamp mode. This is running vertical biamp configuration driving Von Schweikert VR4-III's. I also tried this with Totem Mani-2's. In both cases I asked the speaker mfg if I would be better off using biamping vs one larger amp I was trying to decide if I should buy a larger monoblock Eagle 11 vs using my Eagle 4 amps. Totem said one large monoblock would be best (which I confirmed). Albert Von Schweikert said vertical biamping would be better. The VR4's are 2 separate modules and he recommends passive biamping. I've tried many other amps and none have performed better than the Eagle 4s in vertical passive biamp.

It will be interesting and worthwhile to hear what Snell recommends . . . but I suspect you may have proven the point already.