Server Motherboard Questions

I am thinking about building a new system and I have seen some of these server motherboards that are capable of handling far more memory and multiple processors. I have a bunch of questions that I'm just not exactly sure of when it comes to these boards.

1. Is it just a server motherboard that can use mulitple processors (like dual lga for example)?

2. If so is it necessary that it uses a server processor?

3. Do any of the server boards support things like SLI or Crossfire?

4. I need an audio card slot for my Sound Blaster X-Fi Elite Pro. Do these types of boards normally support that?

5. I've seen some of the server motherboards, like a quad lga Tyan for example, that has an add on card for 4 more processors. Is it common for server motherboards to have this feature? It would be nice to have the ability to upgrade in the future.

Basically, I'm trying to build something really fast because I like to render video and 3D, which is a very time consuming process. I would also like for it to be upgradeable. I've built a ton of systems with regular gaming motherboards. It looked like the server board might be the way to go for speed since it can handle the extra processor and RAM. I just need it to do the regular things like gaming, movies, music, etc, too. It would really be more of a personal computer than a server. I would like to just run Windows 7 on it. Maybe someone out there has built a system like this before and can provide some insight.