mrmonkey, your computer specs are definitely good for any poker site
there is. Very nice indeed
What I'm thinking is, your internet connection could be what makes you lag.
-What's the speed? Do you share with anyone else or are you the only user?
-Do you have stuff downloading while you're playing? (or the other user)
-Are you watching some tv online or some live stream online? (or the other user)
All these things might affect your connection, thus affecting your lag.
Try to have all downloads off, internet browser off, tv/stream online off, everything off.
If there is another user, make sure that he's not downloading stuff or watching tv or any stream online, or simply turn off the other computer for some minutes while testing the lag issue.
Open a table and check how it goes.