I haven't tried a sub yet but sounds like a decent addition for the money. I have not seen any toppers and not worth much to me since it has nothing to do with gameplay. If you are getting Aurich's artwork, you will be very pleased with how it will look. Night and day difference.
I recommend getting Mezel Mod's warp ramp insignia light diffuser. It's only $15, easy to install, looks good, and works as advertised. The insignia is not as bright as the inserts but still much more noticeable than stock. I didn't realize that the warp ramp was even used as a shot in some modes until it was mentioned by someone.
I also ditched the metal washers used as plastic protectors on the slings. They are butt ugly and you can either get clear washers or complete plastic protectors. Cheap and easy.
Last good mod is ditching the ugly, black post rubbers. The ones near the warp ramp get destroyed in a hurry. Get super mini post rubbers. I got the clear ones but you can get different colors. They last longer and stay clean. A little expensive at around $1 each but you don't need many of them.