Biamping help needed

My system consists of older Harman Kardon equipment. My preamp has two sets of outs. My power amps which are 2x100 watts can be bridged mono for 1x200 watts. I am driving B&W CM4 speakers. I currently am set-up in a vertical biamp configuration, which means I use 1 amp to power 1 speaker. I have been told that this is the best set-up when using identical amps.
I am currently looking to purchase a package of cable from Virtual Dynamics. I am wondering if I need to purchase 2 pairs of speaker cable to continue the current set-up or if I should purchase 1 set of biwired speaker cable and run the amps in bridged mono.
I believe the end result of doing this would be to free up one of the outs on the preamp, cut down the cost of speaker cable and interconnects (I think I would only need 1 set of interconnects the red IC going to one amp and the white IC going to the other). Are there any sound advantages or disadvantages to running the system through bridged mono amps and therefore having to use biwired speaker cable as opposed to 2 sets of speaker cable? Any help or thoughts would be greatly appreciated.
If I follow you correctly, you would in fact, free up one set of pre outs because you would only use one right and one left, leaving the other set open. Running in vertical mode works for some people. My experience was different. When I vertically biamped, my separation completely disappeared and I lost all my imaging. Try horizonal also, and see what you come up with. (That would use both sets of pre outs). As for using two sets of speaker cables versus one set of biwired, either way would work, if you have the chance, try them both. Running in bridged mode should give you more power which (usually) will give you better dynamics and more powerful bass.
I've never heard a briged amp under ~$5K sound good, they have all sounded awful really, to be honest. It's a problem with phase I'm told technically, but your ears should be able to tell what sounds better. If your speakers aren't that power hungry and/or you don't play at insane volumes, you may very likely find that just a single amp, ran with a single wire to each speaker, will sound better or at least no worse then what you have now, done with less expense and clutter. Don't realy on what other people say should be ideal, keep an open mind and let your ears be the judge, it only takes a few moments to try the different setups to see for yourself....
Thank you for the responses. I will have to borrow a set of bi-wired cables and try in bridged mono mode and try with a single amp to see what the differences are.

I am thinking of selling my two Harman Kardon PA220's (2x100 watts each) and purchasing a higher quality 100 or 200 watt amp. Does anyone have any recommendations in the $1500-2000 range?
Thank you