Could you use a regular cpu? yeah sure, no problems.
Server style CPUs are designed to handle, and speed up data access. Thus they normally have more cache than desktop cpus.
Also they are offen made with scalability in mind, for example will work with quad board style configs.
I have a server thats an opteron, and my desktop CPU is an X2. If you ask me, they are exactly the same.
For what you want, im sure any desktop cpu would be just fine.
What role is your server going to have ?