hi all, just wondering if some of you guys could possibly give me some advise please:- i own a small video production company and use Premiere Pro CS5 and After Effects CS5 for my editing. i currently use a self built windows PC (dedicated solely for editing) with the following spec and everything renders very nicely and i can happily edit many layers of AVCHD footage in real time, even with effects, transitions etc etc added Windows 7 (64) Nvidia GeForce GTX 285 i7 860 Quad Core Processor 280 Ghz 16 Gig memory 3 separate HDD - 2TB each i currently own an iPhone, iPad etc but have always been apprehensive about buying a Mac due to the different operating system and all my current software being windows. but last week i fancied treating myself to something a little different and purchased a 13 inch Macbook Air........and I've been very impressed! i love how simple they are to use and especially how smooth everything operates. in fact I'm so impressed that I'm now considering changing my editing PC to a iMac. now i know that as an editor the Mac Pro is the obvious better choice over the iMac.......but i just love the look of the iMac, its space saving capabilities and the screen quality is amazing here is the spec of what I'm considering:- 3.4GHz Quad-Core Intel Core i7 16GB 1333MHz DDR3 SDRAM - 4x4GB (i will purchase the memory elsewhere though to save on cost!) 1TB Serial ATA Drive AMD Radeon HD 6970M 2GB GDDR5 Magic Trackpad Apple Wireless Keyboard (British) & User's Guide (English) now when i compare that spec to my current PC's spec then the iMac looks pretty good on paper..........however, i have one major concern the iMac comes with a pretty good graphics card, but its not compatible with the Mercury Playback engine that is a very important feature of Premiere Pro when using the Mercury Playback engine i can place layer upon layer of footage on top of each each to create a video wall, load them all up with a ton of effects and it will still play back in real time without any stutters etc (at full resolution too i should add) but if i do the exact same thing without the Mercury Playback engine kicking in then my PC struggles terribly, lol however, i rarely produce such videos that are so intensive.....so that was more of just an example of the difference between using the Mercury Playback engine and not using it.......but even the more simple projects still slow down quite badly when not using the Mercury feature okay, so to basically try and cut a long story short.........do you guys think that the iMac with the spec posted above would be able to handle my requirements for editing even though it would not be possible to enable the Mercury Playback engine (its only compatible with Nvidia cards unfortunately) as I'm sure you can appreciate, i don't really want to spend a couple of grand on a machine that even though it has a higher spec than my current PC would actually have a lower performance when editing, lol many thanks in advance, cheers scott ps.....is it possible to replace the graphics card in the iMac for a nvidia one?