Power Mac G5 - Could i upgrade CPU to Quad?

Hello everyone. I have a question about upgrading CPU in my Power Mac G5. I have Dual 2 GHz PowerPC G5 and was thining about changing CPU to Quad 2.5. Is it possible? My model is with DDR2 so i assume its late 2005 or early 2006. What i can upgrade? I have 9GB Ram but could put up to 32 so maybe will do

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OK. Thank you for answers. So i'll have to buy 2.5 quad thx