I don't think using the jumper will give you the same results as a single or double biwire will.
The biwire Mont Blanc should be sufficient for the 804's, which don't have large enough woofers to need the bigger gauge of Volcano. You could have the Volcano reterminated as a single biwire, which requires just the speaker end to be done. Audioquest will charge perhaps $50-60, but then there is shipping both ways and the wait involved, although you could have the seller ship them directly to Audioquest.
Volcano may sound better than Mont Blanc, but at what price? Probably double. I think Mont Blanc is as far as you need to go in the AQ line.