Many AGP cards requiring a 12v lead do so by the PSU standard 4 pin connector. If you buy a new AGP card with a 6 pin 12v lead, the card should include an adapter for that scenario. Regarding a psu recommendation, which AGP video card do you plan to use?
i've noticed that you need a special connector for pci-e cards, is that also the case with agp?
and if it is, could someone direct me to a good 600w psu that has such a connection on it?
Badge already covered the agp 4 pin molex question. As for the PS question this was pulled from another thread because I am lazy.
First run the PSU calculator to verify your load. Run it as is, and with the additional components that you might be adding i.e., additional graphics card etc.
Edit: Be careful to only set single processor even thought it is a dual core because it is only one socket. http://www.extreme.outervision.com/psucalculator.jsp
I just ordered this PS it is as solid as a rock and on sale 25% off. It is a little longer, so be sure it will fit your case.
Depending on your specific system components, any good quality 500 to 550 watt PSU with around 30 amps or better on the 12v rail(s) should work fine for you. I doubt your system would need 600 watts. You can use a calculator like this to get an idea of your systems needs. With your 1650 your system would draw under 200 watts at power up and idle.