I suppose ensuring that the supply stays 'above' the amount required, rather than constant is more feasible. 

I use a Q-TEC 550W PSU in my main rig to power a V5MAC, R9500PRO, 1xSATA, 1xATA-100, 2x DVD drives amongst many other components.

For me, it's about making sure there is enough juice in reserve if the machine needs it. 

Very difficult to guarantee that you can keep a constant rate, depending on what your system is doing at the time.

Granted, it is louder than my old 400W PSU but that was expected due to the '150W' increase.  There is also a lot of heat coming out of the back of it.  The interior temps seem ok.  Maximum of 31c (when playing SWAT4 for 5 hours  ).

Still, it does the job. 

But I don't understand why it would be 420W when it is labelled 550W, and there is already a '420W' model (the one you have).

Aha!    Gotcha!   

Learn something new everyday! 

ah,  gamma, i have the same board as gary, i just got the latest bios in it, also has a 2500 barton from first runs, so its not locked, i planning on a whole new record for 2001se with this baby, really for AMD its the way togo, for some reason those first 2500 can really o/c, then a 333 chipset board well make a load of difference, epox is my first choice because they o/c better than any other manufactur for the old boards. this is the one ive got in the modded case im working on.

now intel is my next setup, i found a sweet little mobo that will take the 3.06/533 p4, it has the 2x 3.3v, i got a modded case waiting for trhis setup

so you have to great choices right there, the amd will be faster than the 3.06 if you can get it to run at least to 333 and 2.5 ghz

there is really no reason to hold your card back with a 266fsb, everything ppl say about the 5500 (6000 i cant speak for since i dont have one )  not needing a faster cpu are full of it, if any of you believe that crap than pick a game and use fraps, the 3dfx card might not be doing anymore but the cpu sure the hell must be then, the difference between a 2400 at 266 and a 3000 at 333 is big in game like c.o.d. so to me its about playing games with your 3dfx cards, and you gotta have some fps for that, otherwise put that baby on the shelf lol

i know were all different when it comes to our 3dfx cards, for me, if i cant play my games(whatever they are) with my 3dfx card then its going on the shelf, i'll do everything i can to keep it in there as long as i can by turning the settings down, o/c card,board,cpu, playing at 800 by 600, when these things that i can do will no longer work then i will not have any use for a 3dfx card but for my display(which i like) so i guess what im saying gamma is it comes down to why we have these cards in the first place, if your gonna just play old games than a 266 fsb is fine, but c.o.d. and similar games really play much better upgraded, for myself i cant see playing games at less than 30 fps