Adding to what Dandelion said:
Your PC monitor won't help you unless you want to get an expensive scandoubler. Running all of the classic games will likely run better on a PAL TV set.
You'll be able to upgrade your 1200 to run AmigaOS 4 with a PowerPC accelerator card so don't worry too much about the AmigaOne. I have a MicroA1C with some problems hence I never use mine. The only disadvantages to the A1200 accelerator is speed and cost. There are additional PowerPC accelerator cards in the works, however, so cost should not be a problem. As long as the A1200 lasts you'll be in good shape.
I have an A1200 with a Blizzard 1230 accelerator and 8 megs of RAM. It runs most of the old Amiga software and what doesn't run on it I can run on my MicroA1C or emulate on the PC/Mac/MicroA1C using WinUAE on the PC or EUAE on the other systems respectively.
If you want a portable Amiga you're out of luck unless you buy AmigaForever and install EUAE on your PowerBook. It won't run native PowerPC applications but the rest will be fine.
Park your browser here or AmigaWorld.net and we'll fix you up just fine. (AmigaWorld.net is more AmigaOne oriented so you'll probably be better off here for the emulation and Classic Amiga questions.)
