I've been using LinuxMCE for quit some time now and always had problems with playing HD files from my NAS on MD's. The hardware wasn't the problem, full Gb network, NVIDIA graphics, core2 duo processors and so on. But still my audio and picture was stuttering at times. I tried fiddling with the network settings, on the core, NAS (home build Freenas) and managed switch. No solutions there. I've always used SMB share on my NAS and core to share the files. I read in the forum that NFS was preferable but wouldn't make that much of a difference. I thought I'd give it a try and the lord be praised
all the issues are fixed. Even 1080p is running smoothly now. I don't now if it's an issue with LMCE or my Freenas but it did wonders for me. If you have the option to use NFS I would give it a try.
Just to let you know.