Bi-amping B&W 703's

Absolutely- Your speaker's crossovers are designed with bi-amping or bi-wiring in mind. Bi-amping affords a much greater sonic gain. Just use two pair of identical, high quality cables for the best benefit. A site with some more insights: (http://www.audiotrends.com.au/documents/BenefitsofBi-wiringandBi-amping.pdf)

Theoretically monoblock configuration would provide more benefit as each amps power supply is only responsible for producing one speakers bottom octaves- which are the speakers largest demand on the amp.

If you were going to go active, then stereo amps might make sense.

Here's a suggestion: Contact B&W yourself, and ask their opinion. You'll find that they recommend the owner passively bi-amp when the means are available.

There is no right or wrong answer here, try for yourself- however horizontal biamping as you have descirbed has the least chance of being effective.

Vertical biamping (one amp per speaker) or mono moode on your amps is going to most likely work best. The differentiator being how your amps sound in mono mode versus stereo mode.

Keep in in mind that most amps do not have a mono mode which is what throws a twist into your question.

I dont think that horizontal biamping is worth trying, it just doesnt make any sense.

-Rob