And you definitely want reasonable fast gfx-card. I'd say Mediator busboard and Voodoo3 for it for example. You can also fit cheap network, audio, tv etc cards in it.
Expanded A1200 is ok for many things, but if you want to do heavier stuff like watching movies etc, then you'd better go for Pegasos2. It runs most Amiga's apps and is many times more powerful than any classic Amiga.
