Welcome to cdfreaks, Andy.
I would say that your PC, with Q6700 Core2Quad and GeForce 8600GT, has more than enough power and specs to playback Blu-ray. I wouldn’t hesitate to get a Blu-ray drive and enjoy it!
As for which drive, I see you’re looking at a blu-ray reader (not burner). I usually ask my friends and in this forum, do you have any plan to burn a Blu-ray in the future, for data storage, home made hidef movie, etc? For a few more dollars (well $60 more) you can get the newest 8x Blu-ray burner from Pioneer BDR-203BK, $199 shipped here http://www.newegg.com/Product/Product.aspx?Item=N82E16827129037
There are also other 8x burners from LG, Sony and Panasonic, but currently their price ranging $250 - $400.
If you only want a reader, the LG GGC-H20L is currently $99.99 shipped and it’s one of the highest rating Blu-ray drives. http://www.newegg.com/Product/Product.aspx?Item=N82E16827136154