My wife is a photographer and does a lot of work in Lightroom 4 and Photoshop CS5 using Raw files. This is "crushing" her current 3.06 GHz Late 2009 21.5" iMac with 8GB. So we're trying to decide on a new one while trying not to break the bank. One option I'm considering is the 2.7 GHz 21.5" with 16 GB of RAM. The thing that concerns me the most here is the 5400 RPM hard drive. My understanding is that Lightroom is very hard drive intensive. Does anyone know if this will be a significant issue? Another option is the 2.9 GHz, 27" with 8 GB RAM and 7200 RPM HD. The extra real estate is great, but the biggest issue is speed. Will the 27" with 2.9 GHz and 7200 drive be a lot faster? Where can I get the most bang for my buck speed-wise (processor, RAM, hard drive)? what about the 1 TB fusion drive option for the 21.5 v. the 7200 in the 27"? Which is faster? Would we be better off running a 250 GB SSD externally with USB 3.0 and using that as her primary HD? Is that possible? Would it be fast? It seems like a pretty inexpensive option ($180 for the SSD and $35 for the enclosure) if we found that the 5400 was running slow. We keep almost all her files stored on tradition external drives (e.g. Seagate goflex) anyhow; so she just needs enough space to work on her latest shoots. Sorry for the long post. Any thoughts are GREATLY appreciated.