Second vote for seasonic, never had an issue with them. I don't like to use older power supplies with my retro stuff unless they have been completely serviced and recapped and for most computer psus it simply isn't worth the time and effort if a reasonably priced quality replacement solution can be sourced. Even AT motherboards can be powered with an ATX to AT adapter these days. I have their prime 600 titanium fanless psu as well as a 750w (focus i believe) model and they have not let me down so far.
and yeah Pentium 4 was the worst for heat production and performance, all around crap cpus I don't know what they were ever thinking with netburst architecture I am glad they went back Pentium III P6 architecture and have stuck with it to date (I guess they learned their lesson when AMD was kicking their ass). If you can find a cooler that fits in the lindbergh with a high tdp rating go for it, it will only extend the life of your system. (careful when removing the old one though the cpu likes to stick to it and rip out with it, twist it to break it free from the cpu before lifting it off)