Bi-wiring 804s worth it on long cable runs?

[shep]

I'll try to keep this one within the bounds of the B&W page, but can already guess it might be best answered elsewhere. Need some advice. Leaving cable brands aside, lets say I have store-bought 12 gauge cable (CL rated for in-wall), running 50 feet from my stereo/HT setup in the family room (amplifier is a Rotel RB-1070) to my Nautilus 804s in the living room. I am considering laying a second run through the crawl space in order to bi-wire. Discussions of exotic cabling qualities aside, do others in this forum expect that it is worth it? Does a longer run make this an even better idea, or possibly does it not come close to making up for what I am already losing by having 50 feet of copper between my amp and speakers? Others who have run cable halfway across their house rather than spring for a separate pre and CD player, I await your sage advice.

Setup:

B&W 804
Rotel RB-1070
Denon AVR3801 (serving as the pre for the Rotel)
Sony DVP-NC655P (still saving for that dedicated CD player)
Denon DP35F turntable with Signet MR5 basic cartridge
etc.