I am actually awaiting the components now to do this exact upgrade. I ordered a SSD, I am maxing out the RAM, and I am replacing the original processor with the i7-3770S. Yes, it will be a little warmer, but a good thermal paste and appropriate application of such will help to dissipate that additional heat. It’s not like your going from 55w, which the original one is, to something like 95-110w. I should have the parts within the next few days, I’ll post an update once I am done completing the upgrades.
I have performed the upgrade to the i7-3770s , replaced the HDD with an SSD, and upgraded the RAM to 16GB. The performance increase is very noticeable. The computer operates far quicker, and items load faster. I highly recommend doing these upgrade to the education model iMac EMC 2545.