I think the only thing you'll need to pay attention as far as accessories are anything used specifically with the table. This would include inserts and the shaper fence. i.e. the shaper fence for the model 500 fits only the 500.
Speaking of the 500 system that is what I have and is the same as you. I have the most up to date saw guards and they work well. Won't get all the dust but are safe nonetheless. The front extension is nice as is the wider table. You may also want to think about having two extension tables which would help crosscutting longer boards. I break down sheet goods before I use them on the table saw, regardless of size of table. The only upgrade I don't have is the upgraded rip fence. Might be the next thing I get. Still on the "fence" (pun intended) as to if it's a better deal.
Model rockets! Lots of fun there. I was in Young Astronauts in grade school and we had yearly launches. Someday I would like to buy one of those educator packages where you get 12 kits and give them as gifts to nieces, nephews, and my son for Christmas with the idea of launching them at a picnic in the summer. I figured it would be fun for them to build them with their parents. Call it Uncle Erich's model rocket fun or something.
Happy shopsmithing
-Erich-