When I got my 840pro I benchmarked it against my 470. SATA III vs SATA II. The difference in raw numbers was great. 525/525 read/write vs 300/300. But when it came to loading a game or a level, there was nearly no difference. Some of the games I tested were a second faster on the 840pro, but most had identical times. Both were MUCH faster than the Seagate 7200.10 drive I test against. I would have no problems with anyone putting a SATA III drive on a SATA II board. You won't get the full "raw speed" of the SATA III drive, but it will be much faster than a spinning drive. And the speed you are missing won't really be noticed in real world apps.