iMac G5 PPC Equal Ram?

I have a Apple Certified Refurbished pre-iSight iMac G5 17" w/ 2.0GHZ PPC
its got 512MB RAM in 1 of the 2 slots (im hoping you already know this)






What im wondering is if i can purchase a lonely 1GB to put beside the 512MB or if i NEED to buy another 512 or 2-1GB's to keep it equal

i've heard this before from the Apple customer service, but they also insisted i needed 512mb DDR-Dimm or whatever (which i found out was for the next models of PPC iMacs, they dont support my older one)

so i found this on Newegg.com: http://www.newegg.com/Product/Product.aspx?Item=N82E16820145505


Can anyone shed light on this subject?

Thanks in Advance,
Mac Fan... but ultimately a NEWB

Here are the specs.
http://www.everymac.com/systems/apple/imac/stats/imac_g5_2.0_17.html

Supports 400 MHz PC3200 DDR SDRAM. If installing RAM in both slots, use matching memory for best performance. (2x1GB)
http://eshop.macsales.com/MyOWC/Upgrades.cfm?model=221

A DIY for your iMac.
http://docs.info.apple.com/article.html?artnum=300205

And Welcome to Mac-Forums!

Thank you much.
I also found alot of helpful information clicking on the crucial sponsor along the top, using the mac scanner.