I'm not sure I understand the first question. I am streaming 1080p *.m2ts files that are direct Blu-ray rips with no re-encoding, so if you are concerned about performance it'll be just fine. I have my EX485 connected to my router via gigabit ethernet. All of the clients viewing the media are on the network via wireless N (AEBS). It works great but YMMV as per usual with wireless.
I have not used the feature that you mention, having the server consolidate the media. It gives me the willies just thinking about it.
What are you using to play the .m2ts files, I have found that playing straight blu-ray rips on the current gen mini will cause stuttering at super high bit-rates. I currently use plex and have the most success with mkv in the 10-15 GB range, those never seem to drop any frames but the .m2ts files that are in the 40 GB range constantly drop frames.
I did pick up the ex495 and have started transferring my media to it. I set up the iTunes server but don't like the way the songs show up in iTunes, it is only a list and doesn't include album artwork, so I am probably going to move my library to the MSS and point itunes to that and see if I get a better result that way.