over the past 2 months they've gone to absolute crap..
Psht try the last few years dude.
That graphics card is pretty anemic, too. It may just be getting blown out of the water,
Highly doubt it. I have two friends with the 9600XT, one with the 128mb other with the 256mb, they can handle HL2 just fine.
ATLEAST - 24A on your +12V rail,
Unless you're running SLI with tons of other hardware, a minimum of 20a will be more than sufficient for that setup.
You need to go into the BIOS or use motherboard monitor 5 and monitor your voltages. If you see your +12v line dropping to like 11.5v and below, then yes you need a much stronger PSU with +12v rail, same goes for the others, if the +3.3 is even down at 3v or the +5v is below 4.7v then your PSU is being over taxed by quite a bit.
If your numbers are like this:
+3.33
+4.96
+11.95
then your PSU is right on, and is not being taxed beyond it's capabilities, up to 5% fluctuation is normal, if it hits 5% or exceeds it, is when you start having probs
An Athlon 2600+ XP running at 53C is completely normal, especially for stock heatsink, so all these posts about 'Its overheating' simply arent true...I've had a hotter XP with stock heatsink thats still running strong to this day. I assume it'll hit near 60C on full load, which technically it can handle, but I would indeed suggest in better case flow, colder room in the house, better heatsink or all of the above.