It also depends on the codec the media is encoded with. I convert all of the files to MP4, H264, with AAC audio in first and AC3 audio in second audio channels. I can direct play about 95% of the titles I have on 95% of my clients.
Where things get sticky is transcoding a 1080p video that has 8mbps or higher requirements and I need to get things down to 1.5-2mbps. The transcoding is entirely CPU dependent, and the 50xx series has a somewhat smallish CPU for transcoding. In fact, it's not really capable of doing a 720p transcode with just over 1K Passmarks. Plex's support documents suggest a CPU with 1500 Passmarks for 720p and 2K passmarks for 1080p.
So, which NAS has the horsepower to do full transcodes from Asustor? The only one that can handle either 720p or 1080p is the 70xx series. It has better than 5K passmarks. I've had 7 users streaming at a time, 2 of them 1080p transcodes...)
Without going to this powerhouse, the only option is to make sure the media is as direct playable as possible. MP4 in H264 with AAC audio.
Memory usage when Direct Playing is minimal. Memory usage when transcoding can get out of hand quickly, with more than a single stream involved. I went to a full 16GB for my NAS, and seldom see the memory rise above 20%. When it had just 4GB I was hovering around 40%, transcoding going up to 50-60%. (10% increase, roughly per stream at 4GB. Now about 2.5% per stream at 16GB.)
For what it's worth, I bought 4 sticks of this memory:
http://www.ebay.com/itm/251420608123?_t ... EBIDX%3AIT 2 for my NAS and 2 for my RoG G751 laptop. Both machines love the new memory.
and was wondering about upgrading the RAM 
. Given the unit comes with 1GB, do I need to remove that if putting any more then 1GB in a slot? What I mean is if I put say a 4gb card into one of the ram slots will it operate with the 4gb (4 ignores the existing)? 5gb (4+1 existing)? or 1gb (ignores the new 4gb)?? 
