When i had my TM i found the stock barrel to be fine and i am not sure that you will notice a big difference, i did have the first one tho and since then seen that they all come with the APEX barrels as standard.
It a autococker thread barrel so best bet is to try some out i think the standard barrel was 689 but don't hold me to that.
The main change would be the paint, what paint do you use?