buffering/new server help

Hi;
Ok; I set up an ubuntu 16.04 server/nas at least for me . I came from a emby server on mint 18 cin.
Now on music play back I get buffering at times . an a rather long pause.
htpc is a mint 18 cin desktop kodi 17 with 4 gig 64bit . server is 16.04 x64 on a dual core (both htpc and server are) with 3 gig ram.
htpc uses 120gig ssd. server 1 160gig hd (os) and a 1 tb drive with files.
i have open ssh,webmin,htpc manager installed by atomic script/followed guide on http://www.htpcbeginner.com/.
how can i tweak this to improve performance??
now i can stream with min buffering from internet. ufw setup on all computers.

used both nfs rules in ufw. on htpc and my desktop.
added them in server as well .
server boots up no gui.
router is one floor up in older house . don’t have wire long enough to run down stairs yet.
owner before us had a line running outside to down stairs but it is in next room.
i auto mount nfs shares on my desktop. .
50/% of 1 tb drive used.

any help would be great.
I dont stream to phones etc. amd apu in htpc.
had a nv 720 in the server but pulled it.