Personally, I'd go for one of those Antec NeoHe PSU. Up to 85% efficiency. Believe it or not, my 430w TruePower is only rated at 69%. Tells you how old it is.
But still runs strong after 5 years of 24/7 use. Antec all the way!
Though if price is a major concern, Antec isn't for you. But a good PSU can really make a difference in system stability.
Also, most PC's don't need 400w and even a 350 is sufficient for most. Only reason I bought the 430 so long ago was I was running dual processors and 3 harddrives.
But there's a lot of bargain PC parts out there that'll run just fine for people.
"Using Unix is the computing equivalent of listening only to music by David Cassidy" - Rob Pike