as i recall the stock thermal paste was a bit liquid. I used antec silver and now just recently switched to IC Diamond but my temps did not change from antec silver.
frankly, I would not worry about it. how many case fans do you have? could just be a case airflow issue.
Stock HAF 922 fans (20Cm, 20CM,14CM) but the guy did put the wires in front of the motherboard rather then on the tray and the bottom fans is kind of hide by the cables from the PSU. but then again the cooler is right next to the 2 top fans. Turns out after only a little Prime95 test the temperatures went up to 53 degrees.