I've heard people say a few different times "not to even consider the base imac for video editing". Why is this? I'm really trying to weigh out the needs vs. wants. I don't really even want a 27" display (I'm satisfied 21.5), but I don't want to get less than I need in the computer itself. Processor: 2.7 i5 vs 2.9 i5, how much difference will I really see? HDD: 5400rpm vs 7200rpm, does it make much of a difference if I'm editing footage a 7200rpm external drive? RAM: Will I really need more than 8GB later? I'm currently making due with 1GB RAM, and although I desperately need more, I don't see myself needing that much more. Is there anything else I should compare? I'm not looking for a super editing system, but i'd like to get a new iMac as a 2nd machine to my 07 Mac Pro (two 2.66ghz intel xeon). The most strenuous thing I'll be doing is some 1080p FCP 7 editing, a little photoshop, and some occasional 4k/5k RED footage converting to 1080p (although I don't mind how long the exports take). Can I really justify shelling out $500 more for the base 27"? Or would I be fine with the base 21.5?