I would disagree with you. Dell, apple, etc. Majority of OEM's use crap psu's to save money, you don't see many of their psu's failing. Most of the time its their hardware that fails first. haha. But seriously dude, although I would have researched and picked a better psu, t he one you got should be just fine.
OEMS actually use decent PSUs that can at least (mostly) deliver its rated power. They just cheap out on the Watts and "quality"
With some generic PSU you buy (EG. Diablotek RPM) it can barely do 50% of its rated wattage.
The fact is, when you can get this
for under 50 pounds, getting less for the money doesn't seem so smart.