what exactly are you doing - more detail could lead to better results… are you migrating domains together into one AD (assuming this is a windows 2000+ environment?), are you buying new equipment? is this for websites or a corporate network ?
what types of servers ?
how much control do you have over them & what type of access do you have to them (i.e. physical access or not) ?
I have some really good white papers on server 2003 migrations and domain merging, I don’t do a ton with web though