There is Not a big diff in using a sata III SSD on Sata II. May show a big diff in benchmarks, But in real lif day-to-day usage, not as much as you may think.
If fact the Agillity III (a Low end sata III SSD) performs almost Identical on sata II as it does on SATA III - Even in AS SSD Bench mark.
For the better SSds, I'll use My M4 as an example.
M4 laptop, Samsung i5-2410M laptop.
If you look at the stats Only two would be limited By Sata II.
Most manuf use ATTO as the benchmark of choice, and then quote the Fantastic Sequencial Read/write performannce. BA HUM BUG.
1) Sequencial peformance is the LEAST important parameter for a OS + Program Drive. IT IS the random 4 K that is Important. Do Not misread, Sequencial performance is Important for a storage drive that Has all thoes large Video Files (face it you are NOT going to put many 30 Gig Blue ray files on a SSD), Large cad/Cam drawings, large Spreadsheets, and the 100 Plus family (girly) 10 meg jpeg/bitmap photo files.
2) ATTO is a POOR benchmark for SSDs, it was developed for HDDs. It uses data that is Highly compressable (favors the SF22xx controller Based SSD). Again if you look at a OS + program drive the compression ratio is low. AS SSD is the other extreme, But closer to real life.
My experience, I have 3 M4's, 3 Samsung 830s, 2 Agility IIIs, and 6 older generation SSDs. These are currently installed in 3 desktops (one w/Sata III and two with SATA II) and 2 laptops, one sata III and one sata II.
And Yes one desktop has Intel SATA II and marvel SATA III - and yes I stuck the SSD on Intel's sata II. Stuck the WD SATA III 1TB HDD on the crappy marvel controller. PS WD sata III HDD is a waste of a good Sata III port.