|"....their power supplies are famous for dying early deaths...."|
That applies to their desktop computers only.
Particularly, if the PS brand is BESTEC, they're the worst for that.
There's nothing particularly substandard about the other parts in their systems - in fact, the mboards on their desktops are often made by major brand name mboard manufacturers these days.
If the PS is a BESTEC model it is a VERY good idea to replace it with some other decent PS, because not only do they malfunction more often than average, when they fail completely they are a lot more likely to fry something else, often the mboard!!
In most cases you can replace it with any decent standard sized standard ATX PS with the same capacity (wattage) or greater.
Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.
Don't buy an el-cheapo PS.
See response 3 in this:
If you intend to upgrade the graphics card, or if you might do that in the future, you may need to get a PS with more capacity .....
Your power supply must have at least the minumum capacity required to support a system with the graphics card you are using installed, or the max graphics card you might install in the future.
(Onboard video - video built into the mboard - IS NOT A CARD!)
You can go to the video card maker's web site and look up the specs for the model - often under system requirements - the minimum PS wattage, and, more important, the minimum amperage the PS must supply at 12v is stated. If you don't find that, any card with the same video chipset including any letters after the model number has very similar minimum PS requirements.
If you want to cover any possible video card, a minimum 600 ot 650 watt power supply will handle any current high end video card, or even a X2 card (two video chipsets on one card) or two cards in two slots.