HP Pavilion A527X
AMD Athlon(T) XP 3000+ running at 2.10 GHz:
Advanced 400 MHz front side bus
Socket A
Chipset
Via KM400
The radeon 4670 AGP is overkill and is worth double the price of the actual computer.
The XP 3000+ when released was not bad at all, but now, I am not 100% sure it even has the power to play a 720P youtube video.
With that said, perhaps a used agp Nvidia Geeforce 4 MX or Ti, or a radeon 9600 would do serve it well... It's also they generation of cards that went with the hardware at the time.
Not sure where you are located but I would recommend a new "Old" computer considering I see that budget maybe limited.
I suggest looking within kijiji, craigslist or similar and to get a 90$ to 150$ computer that sports at the very minimum an 939pin, AM2 or LGA775 CPU.
Something with one of these cpus
Athlon X2 3800 to 6000+
Core2Duo with about 1.86Ghz
I purchased a few days ago the following
http://montreal.kijiji.ca/c-buy-and-sell-computers-Lenovo-IBM-E6300-Core-2-Duo-1-86GHz-1GB-80GB-DVD-100-W0QQAdIdZ387097060
I got 2 of them for 180$
The big flaw of the above station is that it doesn't even have a PCIE that is capable of a standard videocard.... But they run great for basic needs or VOIP servers