Hello. I too have a LX200 12". I am pretty sure that the eyepieces you can get are only limited to the Plossol 4000 serries. They are a very good series of eyepieces though. I think you get the whole line of them: 6.4mm-40mm. You don't get the 56mm i don't think beacuase it is the most expensive. Filters. Well you should probably get a red or orange filter for mars and other planets. I have these and it brings out the color dramaticly. Another filter you should consider is a light pollution filter if you dont have very dark skies, i herar theses work quite well. The one i would suggest would be the Series 4000 nebular filter from Meade. If you had the extra money you should get a Hydrogen-Alpha filter from
Thousand Oaks Optical. I have one and it GREATLY increases nebula emissions for stunning optical views. Well i hope this helps you some.
Jeremy