YES YOU CAN,
but we don't know if the fan will spin to out of control because of the fact that the sdd won't be from apple. so we might have to cut the fan wire from the sdd
and also the fact that apple does not enable trim for a third party sdd, so if you want the sdd to go to full potential for your new iMac
you have to download a third party software such as TRIM Enabler to activate it.
this is the sdd that I am putting in mine
http://www.amazon.com/Crucial-128GB-2-5-Inch-Transfer-CT128M4SSD2CCA/dp/B004W2JLB6/ref=sr_1_1?s=electronics&ie=UTF8&qid=1355266202&sr=1-1&keywords=crucial+m4+with+data+transfer+kit