Upgrade storage, nas or not?

Hi all,
Everything up and running now and sorted with nice artwork. I am probably going to be running out of space in the next few months and was wondering what the best solution is. At the moment I am using the mycloud ex2100 for all my needs. But my needs at the moment are limited to local steaming of 1080p with no transcoding. This is going to increase when I move out and I will need it to be able to handle around 3-4 1080p streams at a time both local and remote. It will still not need to transcode as i usually make sure my files play friendly. Firstly, I do not know if the ex2100 is able to handle this, do you think it could?
And more importantly what should I upgrade to, they have the ever so slightly more powerful ex4100, but they have now released the extremely more powerful pr4100, which is unfortunately a lot more expensive! Would you say the ex4100 could handle my needs or should I try and find the extra money for the pr4100? Or would it be better to go for another brand nas? The Other option would be a pc with das, but if I went down that route I would need a small yet powerful pc that wasn't obtrusive. Thanks in advance :)