I wouldn't trust my new PCIe card to anything that isn't 24-pin. PCIe draws a lot more power than PCI/AGP, and needs a more stable supply of it without robbing the CPU of a good supply. That's the whole idea behind 24-pin PSUs, and it's why servers have been using them for a while (i think PCI-X is the same way). If you are throwing an X300SE and an A64 3000+ in there, at stock, i'm sure you'll be fine. Somhow i doubt that, though, so I'd pony up for a better PSU. Luckily, pretty much every 24-pin PSU should be adequate, since they are mostly high end PSUs. I've heard the Antecs are great, and i think they have a 480W that's not too expensive. I personally love my Vantec, it's pretty quiet and has plenty of power and airflow. I got it for $90 at newegg. Look at it this way - clearly you waited a while to buy into a good, stable platform to upgrade to, and i imagine you'd like to get an upgrade out of it. Well, you'd better believe that by the time you upgrade to a dual core A64, or an extra 2GB of ram, or a new 7600GT or X900XL or whatever, your PSU will be dead in the water, so why not just get a good one now, then it's one less thing you'll have to worry about later.