Ok, well I doubt memory will be the bottleneck.
You have SD card and CPU blowing up in flames way before the RAM becomes an issue specially with 512MB.
I think these small computers are surprisingly well balanced to become part of distributed HTTP server solutions!
With that I mean that 100Mb/s, H3, SD card and 512MB RAM are all about the same place if you write minimalist software.
We'll see how it turns out.
btw, thx for second release and jessie!