SSD with firewire enclosure?

I would like to replace the hard drive in my mid-2011 iMac with an SSD but understand there are some issues with the fan if this is done. I was, therefore, looking to get an external 512 GB SSD instead. Since I only have USB 2.0 on the iMac, I was looking to use the Thunderbolt port. Unfortunately, until OWC comes out with their firewire enclosure (no ETA, I asked), it leaves me with firewire 800 as the only "fast" option. (I considered the Seagate Thunderbolt adapter but the smaller one only works with 256 GB and smaller drives and I'm not really interested in the larger one for price and size reasons.) My question is whether I would notice any significant difference in speed over my standard hard drive if I used the SSD with firewire as my boot drive?