i have the same configuration, 4Tb, Raid5 and firmware 2.2.8 and have no noticeable problem with my multimedia device DVICO or PC (Windows media player) or laptop (WMP)…
Have you checke the network configuration ?
i remember i read a post of someone having this kind of “pausing” problem, and it was linked to the wireless card …
I had the same problem when playing music back from my central ITunes library on the exact config you have, its great in theory but flawed in practice! I tried everything to fix it but in the end I just moved it back to my internal drives