Revision C and earlier of the Soyo does not run Coppermine at any speed. Most revision D boards don't work either. Revision E work fine and probably should work fine with any multiplier, since the motherboard multiplier setting is ignored with these chips. The revision is stamped on the corner of the board (I think on the underside).
I ran a Celemine 533A (8X multiplier) at 960 MHz on the Soyo (revision E).
I've never used the BX6 2.0, but it should work fine assuming the BIOS are up to date.