What applications are you running on your system?
I mostly watch digital TV (I have DVB card and watch TV on it and use it like a modem :> *from 3am to 6am I get speeds of 40-60kb/s and with country where people only have 56k dialups this is premium*)
I play games occasionaly, I am not some passionate gamer, I use cheats

... I play them becase I want to admire the graphics and the degree of technology advancment, and I always like to check what's all the bragging about
I websurf a lot, and I have around 20 IE windows and 10-15 Opera windows opened all the time, Download Accelerator, Du meter etc...
I make webpages as a hoby, mostly in notepad and in macromedia dreamwaver, little less photoshop editing...
Listen to mp3s in winamp and watch a lot of Divx movies :>
that's mostly it, I don't do professional work.
I decided to hold back on upgrading because I think I've accomplished a well balanced system, IMHO it is really hard to do that, make all the components work without larger issues, have a decent speed, have estethics and mostly I like to keep my system silent.

And now it is silent, it works with closed case
with temps from 42 to 52 C max, using Zalman's CNPS 3100 gold and 2 extra 80mm fans on the case.

Also, check out what a generic 250W psu holds
-TBird 1.4 Ghz not overclocked (I cant overclock it on my motherboard)
-Gigabyte Ga-7vtxe kt266A mobo (very stable but almost zero overclocking *it crashes when I overclock so I've stopped*)
-256 mb Samsung ddr ram (sandra reports the chip as Micron) *cas 2, 2T , no interleaving*
-HDD Maxtor 20gb ata133 (hdtach 2.61 score of : 42000average read under winXP, and sandra's score is 26200)
-HDD IBM 75x Gxp which I decided not to use and keep it just in case

because it is little slower than the maxtor, and I dont use more than 20GB, I do a lot of backing up on CD's
- Gainward GF3 GoldenSample (Can hit 280/590 stable but I drive it at clock speed, I dont want it to die on me and I dont want to use extra cooling because of the noise issue
-DVD Hitachi 12x40
-CDR LiteOn 12x10x32 (I don't need anything faster, this is great for me, I use noname mediums and I record audio at 12x and they work in every diskmen afterwards
-Monitor 17" Ctx pr705f 1152x864 32bit at 85Hz (I run it mostly on this res)
-SB Live 1024 value
-Teac 2.1 powermax speakers (for the rear channel I use some speakers from my 20 yearold Shneider radiogramaphone
-DVB card, SkyStar 1, for watching Digital satellite free channels (~100 channels, I watch mostly the music ones, MTV and Viva *I live in Macedonia*)
-56 PC tel PCI modem
-Realtek ethernet card to connect to my sister's PC
-Printer Oki...8wlite
-wireless chikony keyboard on which I've installed a wire to a DC adaptor because it was eating batteries every 2 weeks or so
-MS Intelli optical mouse

All my components work on generic 250W psu, no problems at all, everything is virtually silent :>