Upgrade to Vista? Are we on drugs?
Why would anyone want to buy Vista? At those prices? Especially if you are a business?
And what security? Don't move from XP to Vista, go to SLED, security, ease of use, cheaper, excellent support, no steep learning curve and works on current PCs, no fancy hardware upgrades. Or if you've got money to burn, don't waste it on Microsoft products or buying new Vista ready boxes, try Apple's Xserve for security, support, ease of use and sheer elegance.