Thanks so much guys. You confirmed my doubts. If I can't justify $400-ish for the Crucial at this point (which is the best I could find). What if I were to get only 256GB? They are going for a lot less - $185 on Amazon. Would this make a huge difference or should I not bother (or get the 240GB OWC mercury)?
To clarify, I am a cinematographer making TV commercials and music videos etc., so I use my MacBook Pro to edit this stuff and I hope to get an external monitor before I become cross-eyed...

I bought the 16GB memory to improve editing/render times and I hope to get an SSD and keep the regular Drive with a data doubler. My understanding is that I should put the operating system and programs on the SSD and keep the optical drive for files o make the whole thing sing?
Just so you know, you can not put a modern, SATA III 6G SSD in the optical slot, only a SATA II 3G or a normal HD. Put a modern, SATA III 6G SSD in the main slot for the best performance for your system drive/applications. You don't need 500 gigs here, just get a 250 gig SSD. Forget this Toshiba other than as a second drive.
http://blog.macsales.com/10433-macbook-pro-2011-models-and-sata-3-0-6-0gbs-update-5272011
I'm an Avid editor running an early 2011 thunderbolt MBP 17" with 16g ram.
I just put a 256g Samsung 830 (great deals around for this proven disk) in my main slot, and my original 500g HDD in the optibay for my extra data.
However, working with HD video, I aways use external storage and not the internal, and that is where the thunderbolt pays off. I don't know what you are shooting on, but besides that second monitor you should explore Thunderbolt RAIDs for i/o speed.
RAM is always important, but your render times are more affected by CPU cores than RAM.
For me, I've been tempted by this Toshiba offer for my second drive because I can only put a SATA II drive in the optical slot. This would allow me to be completely SSD. However, If I had a 2012 MBP, I wouldn't consider this drive at all, and I woudn't consider it in the main slot of your laptop, as it won't take advantage of the speed improvements there.
Because Samsung have moved to the 840, there are lots of deals on the Samsung 830s, a proven Mac OSX drive
I can talk you through the upgrade process, which is fun