Newbie Questions: Which Arduinos Support Multiple Communications?

I apologize if these are obvious answers, but I'm still learning! Here is a block diagram of the system I would like to build:

My questions are:

  1. Which Arduino would be best suited for the "Remote"? It needs to communicate over SPI and TX/RX. I'd also like for it to be a simple and small as possible.
  2. Which Arduino would be best suited for the "Base"? It needs to communicate over Ethernet and TX/RX.

I appreciate your comments and feedback!

Can be uno or equivalent (328P based) on both ends.
RS485 is separate chip, like a MAX488.

How many relays, what kind (SPST telecom relays for example), will they need a coil driver like ULN2803 or high current shift register like TPIC6B595?
That'd be a fun little board to make up, similar to this:
This had 5V coil telecom relays and RS232 for 1 com channel and a USB/Serial adapter for a 2nd com channel. One ATmega1284 for the interfaces, so just the 1 IO chip needed - replace that with RS485 driver and you'd be golden!

Arduino with ethernet shield for the Base.