[Build Help] Looking to migrate from Apple hardware, and would like input on building a professional rig for everything from 3D animation to audio engineering to software development. Would love any advice you guys can offer!

First and foremost, I'd like to ask that people refrain from any kind of fandom. I love Mac OS. I love Windows 7, and I love Ubuntu. This build I'm spec'ing out will have all three as boot options.

My reason for leaving Apple hardware is due to their waning support for professional users, and instead catering to people like Paris Hilton. I do NOT consider a laptop with every fucking component soldered to the mobo a "Pro" computer. It's an embarrassment what is happening to the Mac line. The only moderately modular machine they still have is the Mac Pro, and all the talk about how upgradable it is is just a bunch of lies.

So I'm looking for a build that is reliable, high-performance, and has plenty of room to grow. It would also be nice if the upgrading process was fairly easy. I'm looking for something with performance similar to a Mac Pro or a Boxx system (yes, I realize a Mac Pro is basically a low-end Boxx, I'm not looking for something with 4 GPUs and 64 CPU cores and 128 GB RAM). I need a beefy, no bullshit, professional rig. It can be ugly, it can be loud, it can be big. It just has to do (almost) everything. Oh, and no stupid LEDs unless it actually looks uniquely good.

EDIT: Great questions, thank you for helping me refine.

PRICE RANGE: under 6k would be nice. I'm using this professionally so it's an investment. Obviously I'd like to save money where possible, but I intend to make money with this thing.

OVERCLOCKING: maybe, if the method and hardware in question will be guaranteed safe. I don't want to melt the core(s) of my financial livelihood.

WHAT IS IT FOR: 3D animation, making video games, making music, converting media, writing software for the web, desktop, and mobile. All things Adobe, various IDE's, Logic Pro, Final Cut, Maya, Blender. It's a workstation. Not a toy (though we will be making / playing games on this thing).

OTHER GENERAL SPECS: Lots of ridiculous IO: USB3, FW800, Gb eNet, Thunderbolt (or equivalent if possible / available). Multi-core, Multi-chip. Either dual A- GPUs or single A+ GPU. RAID. Dual Blu-Ray writers. A really nice sound card (which I know little about).

Thoughts? Thanks in advance.