From: Telford UK
I have to set up quite a few of these scenarios and where available or applicable I always use an enterprise CA?
Yes there are obviously differences between stand alone CA's and Enterprise CA's, but do you know why you want to use a Stand Alone? What's your reason, and by this I mean what's your reason? Not just because you read in a KB article? There must be some justification on your part to deploy a CA in a particular manner.
I would as no doubt Tom would tell you to as well setup the array as Domain Members.
Yes there are microsoft articles that suggest being in a workgroup is better for security, but you find some very thorough reasoning on this site and some others over why domain membership actually provides a better security model for your ISA servers.