Personally, I would, if I was spending $1,000+ on a set of really nice speakers. I figure an extra $20-50 to biwire at the very least would be worth the peace of mind... that is, unless of course you spend top dollar for primo wire, but than again if you're spending hundreds of dollars for speaker wire than you're worse than me for thinking biwiring may possibly help. Heck I'm biwiring w/ 2 sets of 10 gauge wire on $150 speakers. I only paid $3 for 30 foot reels of that stuff though... a lot better quality than the home depot 12ga stuff, not even considering the higher gauge rating. Too bad I can't get deals like that anymore
I am obtaining exceptional performance with a single set (not biwired) of Audioquest GR8 (10 gauge) speaker cable, which connects LSi-25s to a McIntosh MA6500 integrated amp. Smooth as silk, clean, liquid, and detailed, with imaging and soundstaging that make the speakers sonically disappear from the room. I'm extremely picky when it comes to this hobby, but I could not be more pleased.
I had some extra wire so I biwired mine. Did I hear a magical increase in music quality? No. The difference was so subtle that I could barely notice any difference at all. I guess the best thing to do is try it if you've got some spare wire laying around, but I would not recommend spending a large amount of cash on Biwire cables.