Dfinitely You only need one machine.
Just add at least a 68030 @50mhz and 32mb
WHDLoad enables old demos to run from Hardrive and fully compatible! nothing is impossible now. Preferably an AGA machine like the A1200 or A4000..definitely much more desirable as you have more games and demos and Screen modes that look nicer.
And maybe some people are not aware, but they do Have WIFI drivers for the Amiga..but only the ones with a PCMCIA port (A600 and A1200)
Get the largest HD you can get......make at least 8 partitions..........that last 2 for MacOS and Linux (Redhat or Debian, FreeBSD)
You can run MacOS 7.5 pretty good on a 68030 Amiga.