Negative on the 6(7). You would get 5 on the charge. The extra attack for 2 weapons is already counted for. The special weapons thing is basically talking about power fists/lightning claws, and thunder hammers. Lets say you have a plasma pistol and a power fist (as my devastator Sgt.) He does not get the extra attack for 2 close weapons, even though a pistol counts as a close combat weapon. On the other hand if I had 2 power fists he would in fact get +2 on the charge (or with 2 pistols). Basically speaking you do not get another extra attack, you simply get your base (3) plus 1(4) and plus 1(5) on the assault. Which is still gnarly because you get an extra attack for every unsaved wound and get to re-roll missed wounds.