Playing around with Assembler and Processors

[Coward]

Hi!

I am a hobbyist DOS programmer on my hold hp200
palmtop (Intel C183 7Mhz CPU) in C, Basic and Assembler.

I've been coding assembler mostly for fun, and I would
like to dive deeper into the cpu / ram / io or hardware
world by setting up my own little computer and coding
some more assembler on it as well as attaching simple
home brew IO Devices like a temperature sensor etc.
From seaching the WEB, I came to learn that there exist
lots of tutorials for both hard- and software realization
using the Z80 Zilog CPU.

The Z80 architecture looks indeed very appealing for
programming and learning. Yet I am looking for a more
advanced CPU (wider and more gp registers, more speed
and wider busses) that could still be run as a portable (
read: low power consumption) device with my self made
IO devices.

The eZ80 and the ARM family processors look interesting,
but I cant find a great deal of fan/support/tutorial sites
for playing around with such a relatively new processor.

Maybe you can give me a hint on this matter? Have you
beeing playing around with your own CPU-RAM-IO setup
using a newer processor? Which one was it, and what can
you say about your experiences with it?

Any advice on this is welcome!