Thinking about Thinking about Computing

Mr. Kangas brings up some good points on my post on computing. Why get a world-dominating computer?
Is it necessary? Will it keep me from murdering my monitor in a fit of render-time pique?
He's right about editing certainly. We do not need an absolute top-of-the-line computer just to edit picture anymore.
Unfortunately I do three things which will, within five minutes, bring any computer you throw at me to its knees:

1. Sound mixing
2. 3D rendering
3. Compositing

The gang in Android Insurrection.

Looking at these things backwardsly:

• When doing a complicated composite with a lot of nesting of images and color-corrections and keying, it gets real irritating real fast when you can't see what you're doing. In fact, I accidentally rendered this particular shot at this size. How? I'd switched the quality setting in AfterEffects to "one quarter" just to have a prayer at retaining my sanity when doing a bit of rotoscoping.
• I'm also tired of the render times involved in lighting 3D models (which is the step before compositing.) It makes re-lighting quite tedious to have to wait a couple minutes to see what, say, turning down the sun does. 
• Honestly sound mixing is the least critical thing. After all, I can pre-render or "freeze" tracks with a lot of effects on them and then easily go back and make changes and then re-freeze the tracks. But it is certainly nice to be able to play 24+ tracks with loads of effects and such without the computer hiccuping.

Here's a computer company recommended by Samplitude folks, Reyniers Audio.
I'm not entirely sure I care about having a computer that has an operating system specialized toward audio. With enough RAM and other horsepower I don't think that an image on the desktop is going to make that much difference really.
One thing my buddy Mitch suggests is to use one of those solid-state flash drives as your system drive. He says it speeds things up quite a bit. So yeah, I'm gonna look into that.
In any case, the big question is whether spending $5,000 or $6,000 on a system -- even if it's (and this is a liberal estimate) twice as fast as a dual-quad-core with 8GB of RAM -- will be worthwhile. Sure, I'd love to see multi-layer AfterEffects compositions play back in real time but I doubt that'll be coming down the pike for another 10 years or so.
Meh.