Well, I've been building PC's for about 15 years. It's certainly possible to have a 100% rock stable o/c. As the above poster mentioned, it just takes ridiculous amounts of testing and stress. I use LinX, for 4 hours or so, it's much more stressful then Prime95, and will spot error's alot quicker. When that has passed, I use 24 hours of Prime95 BLEND. If that passes I use OCCT power supply torture test. Which is a combination of LinX and Furmark, it's absolutely brutal. Putting max load on the PSU, Video card, AND CPU. I only run that for a couple hours. I have not had a bsod since i finished stability testing.. not one. That was a couple years ago now. I'm hardcore when it comes to stability, if I get a BSOD for any reason I'm already tearing my system down to figure out What, because that's not normal, ever.
All the above said, I can certainly empathize with someone who just does not want to go though the hassle, the above took me a couple weeks of trail and error, logging settings, what works what don't etc. And it's not something I do to my family's PC's or friends, because it can be more trouble then it's worth.
With regards to performance, the difference can be dramatic, depending on usage. If your just doing word processing, browsing the web, and email, it's not going to matter if it's 1.5 ghz or 4.5. If you play games, encode video, or do lots of compression, photoshop, etc it can be a large difference in performance. I'm sitting around a 52% overclock, and the performance seems to scale pretty matter of factly.
AMD has made great strides with SLI in the last generation, if you read the reviews you will see that SLI scaling is at something like 90% efficiency now.
I have derailed this thread a bit, and it's my fault. Sorry about that guys. This PC talk is pretty irrelevant.
Naim. Thanks for your comparisons, also NwAVGuy has some good reasons not to use balanced connections, it's in his blog. Expensive, with no benefit, and sometimes a disadvantage. Also if you like the JDS labs faceplate, they sell it by itself for 10$, should be a super easy swap.