Is Bi - amping worth the trouble?

"Headroom" usually relates to the extra energy the amp has available to deal with (loud) transients in music without clipping.
Back to biamping --
a) I wouldn't have much to add to Sean's post above.
b) A quick reference of what you may expect with "passive" biamping is given by warjarret above. The result doesn't justify the cost -- esp. when compared to normal biamping (i.e. amp directly driving the drive units). That's a different level altogether.
...Unless you have a notoriously underpowered amp -- which you don't.

If V Scheik really means what he says about these spkrs having been designed for bi-amping, then he can provide you with the cross-over schematic, and you can take it from there.

Undertow -- that's actually a very good plan! Go for it, Blindjim...

Quite honestly, i'm surprised that nobody has done anything like this

Sean, FM Acoustics does this -- but for tis own products.

As you note, the designer hasn't published anything on this.

BUT, if you buy a complete system from FM (i.e. electronics + cables), that whole transmission line is optimised.

You can even buy speakers (made by someone else ASAIK) similarly "optimised" for the FM amp + spkr wire used. HOWEVER, I understand that the recommended solution is active multiamping... of course, one can order the spkrs with a passive xover in which case the spkr cable supplied is different (obviously).

So, the transmission line is purportedly optimised starting at the source output cable. Since FM's preamps allow some variability in their input impedance, this line can be tweaked soemwhat further upstream.

One snag is, the wires must be specific in lengths (apparently a small variability is OK). Another is the cost -- $~+10-15k per component: this may not look ruinous for some, but for a vinyl addict doing the simple maths, it adds up: Pre + phono+power amp = $+~40k. The cost of cables is minimal apparently:)
Oh yes, I forgot: you also need spkrs...

Oh yes: I actually listened to such a system, vinyl source -- with different spkrs. Admittedly, impressive, very impressive.

Blindjim -- you've measured that ~3dB loss, in what? Or is it an overall, ball-park figure in resulting spl?
I'm curious, thanks.