ECS Agnus introduced the ability to switch between PAL and NTSC in software and expanded the maximum amount of chip RAM to 1MB (2MB later on with the 500+, 600, and 3000). ECS Denise added the SuperHiRes, Multiscan, and Super72 screenmodes.
Odds are good you already have an ECS Agnus, in which case you should just be able to pop in some trapdoor RAM and get 1MB of chip RAM. Type 'avail' in a shell to see how your machine has configured your RAM. If you have WB 2.x, run ShowConfig to learn more about your chips.