Which SSHD should I upgrade my 24" iMac with?

Hello Guys,

I have a Early 2009 24" Imac (2.66GZ, 4 Gig Ram, 640 Gig HD) and Im doing a refresh for it. I already purchased 8 gigs of ram, but I am looking to replace the hard drive too.

I have been looking at an SSHD, and I think this would be my best bet, as I do some light gaming, as well as some video/ pic editing. I saw the fire cuda one, but Im not sure if they do SATA II anymore. Im also not sure how big my bay is ( I think 2.5").

What will I need to do this transplant? Is it worth it? I think my thermal sensor will work? I heard the late 2009 you need to buy another one.

Thanks for the help!