Resolved Which solid state hard drive can/should I buy?

My motherboard is the EVGA X58 SLI LE and is about 5 years old. It has 6 SATA II channels that are rated at 300Mbps. My primary HD is a 300gig WD Velociraptor.
Most of the SSHDs that I see for sale are SATA III.
Can I use them, or do I need some adapter, or should I be looking for an older generation SSD?
Also, is it worth the money/effort?
I'm running Win 7 64bit with a 1st generation Core I7 processor.
The Velociraptor gives me a performance rating of 5.9 whereas all the other ratings are 7.2 and above, so it is the bottle neck.
I did look for and read a few of the related posts, but they are all from 2013.
Is the Samsung 840 still the one to get, or is there a new drive out there that is the new recommendation?
Thanks.

 

Thanks for your reply, Evan. I bought a used laptop that happens to have a SSD, so I guess I'm just a little impatient when it comes to boot time on my desktop. I can live with the velociraptor drive, but I guess one can call it a sickness(upgrade-itis?)-and the alternative would be to spend the money on a video card. I suspect that the SSD "upgrade" is the biggest bang for the buck. I think I'll go ahead and get the Samsung, though for around $110+/- I could get a Corsair, or some other one. The benchmark that you mention, is it at Tom's Hardware Guide? Thanks again for your kind attention. I appreciate it.