If you like classics get an 1200 with an accelerator. Individual Computers 030/42Mhz are new and are perfect to enjoy classics (WB, WHDLoad games, some demos...). If you really want to play latest 060 demos and you don't mind paying up a lot for an old accelerator you should get a Blizzard1260. But that's not usually the case, many people is fine running demos on WinUAE*or playing the videos.
Buying an A4000T and upgrading an A4000T to be able to run OS4/MorphOS*will be quite expensive and will be just a toy because it won't provide a "modern" experience.
The cheapest option to try out MorphOS is downloading the ISO and trying it out on some G4 Radeon equipped Mac. Any G4 Mac Mini will do. G4 Powermacs are cheap too. Latest powerbook G4 model is also a very good option if you need/prefer a laptop. The MorphOS*ISO*you download is the complete OS and allows you to do everything you need (you can install it, you can run it from the cd...). If you like it you can register your machine from MorphOS register tool and a key will be sent to the email you provide once you perform the payment (111Euro right now although older machines like powermacs, peg1, efikas will probably be cheaper after MorphOS 3.0 is released. You pay through paypal). If you don't want to register your machine a requester will popup when you have an uptime of 30minutes and the system will slow down until next reboot.
If you want to try out OS4 you could also get a Pegasos2 machine since it's both cheaper and faster than newer machines and also allows you to run MorphOS too.
My advice: get an A1200 with a 030 accelerator and the latest Powerbook g4/1.67Ghz (or a Mac Mini) with MorphOS.
