Old or New Geneation iMac?

Hello everyone
i am a holder of a macbook pro 2.2 core 2 duo and i am in the process of getting an imac 24 inch. i am really confused on which one to get to be hoest. at first i thought i should hget the top model the 3.06 but thediference with the 2.8 isnt excactly huge. so after weeks i decided to get the 2.8 with a 500gb hard drive(another dilema is to get or not the new graphics card)
ill need to say that i dont play any games and the reason i was thinking to get the new card is to stay uop to date so as to have a machine for a couple of years. I am not exactly doing much of video editing or digital photography and all my needs are basically covred while i am using the macbook pro.
My new dilema nowis:
maybe it is better to get teh old imac 24 inch?with a 500gb hard drive and the old graphics card? i mean its costs 600euros less from teh 2.8 with the new video card./ tyhis means i can have more money to upgrade the RAM and get a drobo share for external hard drives..
what do you sugest?

Save some money and get the cheaper mac - you will still have a great machine