I recently got my first iMac, ex demo unit, 2.4GHz, 4GRAM running latest OS. It is currently fitted with the 'standard' ATI Radeon HD 2600 PRO 256MRAM. For the past few years I have been building my PC's but have never tackled upgrading the iMac. I use my iMac for general everyday computing, some photo editing as well as gaming. Is it worth upgrading to the GeForce 8800GS and if yes, what is involved in replacing it. I have not even yet seen the innards of an iMac Any suggestions and advise is appreciated, thank you.