Ive saved up enough dosh to replace the speaker in my Classic 30 with a Greenback. I called Marshall Music and got a very decent price, but he said he can get the G12-M 8 or 15 Ohm verison which is 20w? Browsing Celestions website I see there are 3...
G12-M 'Greenback' 25w 16ohms 12" (the one I want..)
http://professional.celestion.com/guitar/products/pdfs/G12M%20%27Greenback%27.pdf
G12-M 'Heritage Series' 20w 8 or 15ohms 12" (what he quoted me for)
http://professional.celestion.com/guitar/products/pdfs/Heritage%20Series%20G12M.pdf
G12-H 'Heritage Series' 30w 8 or 15ohms 12"
http://professional.celestion.com/guitar/products/pdfs/Heritage%20Series%20G12H.pdf

This guy is running the first mentioned one.. I surely just going to pop the 20w 15ohms in no time
G12-M 'Greenback' 25w 16ohms 12" (the one I want..)
http://professional.celestion.com/guitar/products/pdfs/G12M%20%27Greenback%27.pdf
G12-M 'Heritage Series' 20w 8 or 15ohms 12" (what he quoted me for)
http://professional.celestion.com/guitar/products/pdfs/Heritage%20Series%20G12M.pdf
G12-H 'Heritage Series' 30w 8 or 15ohms 12"
http://professional.celestion.com/guitar/products/pdfs/Heritage%20Series%20G12H.pdf

This guy is running the first mentioned one.. I surely just going to pop the 20w 15ohms in no time