Ahh, I gets you. Of course, the other question is why on earth you're still buying (in 2011) monitors with only VGA ports. All the ones I've bought for the last 5 years or more have had both VGA and DVI ports on them - and that includes the cheap ones at work!
Still, looks like your only options are to replace some of the monitors with DVI supporting screens, or buy some graphics cards which support dual analogue outputs. ---
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