It didn't appear that all of your questions were addressed...
- This is a 4 channel DMX device, right? So it can be daisy-chained with other DMX devices like LEs, etc ?
- What is the fourth channel for? It says "RGBW", W means white, right? Why do you need that? 255,255,255 gives you white.
- 12V AC transformers (35W per Aether II) - got that part from the Wiki
Yes, a 4 channel DMX device that can be daisy-chained with other DMX devices from DLA or other vendors.
The 4th channel is W. It is a stronger, purer white, and it is better than the mix you create from 255,255,255
Yes, 12V AC (not DC) Use a landscape lighting transformer that you'd obtain from Home Depot or similar. One unit can power multiple Aether2s as long as you do the power planning first.