Biwiring seems to fall into the great cable debate
Some people swear by it while others sneer at it. In my own limited experience with it there seemed to be little or no difference when doing it (just like when I tried different wire for speakers or interconnects). While there seems to be little basis in fact for a benefit, it does seem to me that it's worth trying if you're interested and it needn't cost a lot. Just get some decent speaker wire from Home Depot or Lowe's (where you can buy it cut to length for cheap) and give it a shot. If you hear a difference, then great, and if you don't hear a difference then you're not out a lot of money. People who advocate biwiring generally cite things like increased detail and more open sound but the differences seem to be subtle at best (unless, of course, you can hear them!). Personally I think speaker placement and room conditions will have more effect on the sound than biwiring. Hope this helps a bit.
Gary