Justification for IPS purchase

Hey guys, I have recently completed an evaluation of 3 different IPS devices. ISS proventia, Juniper IDP and McAfee's Intusheild. The ISS product was hands down the best and worked out to be the cheapest. OK having said that I know have to convince management that this purchase is worth it. Any suggestions on how to convince them? Does anyone know where I can find statistics on vulnerabilities? We are a microsoft shop so I am going to try to look for info on trends or stats of MS vulns or expoits overs that last x years.

Thanks in advance for you help.

Perhaps compare the costs of a virus outbreak to the cost of the purchase. You can embellish worm costs to extremes and "forget" to leave in maintenance costs for the IPS.

Just make the report pretty.

I am sure that the Account Manager at ISS has a lot of documentation to use to pitch the IDS with your boss.