Lanthanide made most of my point for me, so thank you to Lanthanide.

I've worked with a lot of computers in my time, and none of them have ever sparked into flame. Even PSUs dying doesn't happen as much as you'd like to believe. OEMs may use generic names(or names you're not going to recognize, perhaps) but that doesn't mean these PSUs are suitable for the machines they are putting them in, or are even terrible. I wholehartedly support not buying shitty 25$ PSUs with advertized wattages of 650+ or the like. But I don't think the same risk is involved when looking at OEM machines. I've worked with a lot of machines the last few years, and I just think this "PSU catching on fire ahh" business is a bit exaggerated, that's all. For the record, the only info I could find on System76 PSUs was that one of their higher end models shipped with an Antec Earthwatts 650w. This was around mid 2009.

I wasn't really referring to PSUs anyway when I spoke about "sweating the numbers". My statement really was referring to things such as RAM. You're not going to feel a speed increase from something like a frequency bump. It's not the end of the world, that's all, and it just seems like people on this forum stress out/emphasize numbers too much, when in reality, unless you're doing things like crunching numbers you won't be able to tell the difference.

CPU quality doesn't matter. It's rare to get a bad cpu.
ODD is old technology and all the same.
HDD is finicky, and there are a few brands to stay away from if you want the best, but if you just want some thing slow that works, any will do.
RAM quality barely matters. If it works, you won't notice a difference in speed except through artificial benchmarks.
Graphics quality barely matters. Certain brands have better warranties, but in general, everything is about equal.
Motherboard quality matters less than it has in the past. In the early 2000s, many PSUs and motherboards were put together with bad capacitors, which were made in china and taiwan using a bad formula. Most newer motherboards do not have these, but they plague the cheap OEM computers. Nowadays, the brand of motherboard and type of motherboard you get matters less, though it makes little sense to stick your i7 in a cheapo motherboard, and likewise your pentium in a $400 4x SLI.
Power supply is the biggest point where quality truly matters, though it is somewhat misleading. 80+ power supplies go through a semi-rigorous test under optimal conditions, and will be usually good to go. However, those not certified could be poorly designed or outright lie about their wattage. A 500W PSU that burns every time you draw 360W from it is not a 500W power supply. It's a bad design, not only because it burns (you can make it so it shuts off before it burns) but because it lies about its wattage. However, who actually uses 360W of power? No OEM with onboard graphics will come anywhere close. You'd need a mid to high range graphics card to come close to that mark. So that shitty 500W PSU will work fine for anyone using something less than 360W.

So if your computer works, it doesn't matter on the quality of the build, just so long as it works. By increasing the quality however, you are also increasing the likelihood that it will not break, and will be able to handle the future better.