kudzu

Have you make a "sync" after dd ?
 
I see also sometimes recommendations to wipe the cards (dd if=/dev/zero of=/dev/sdX) before copying an image. I never do this, as I never found a justification to do it. But I also sometimes copy images that will not boot ...

Usually, such issues can happened when doing a "dd" while sd is still mounted with previous partitions.
Making sure no partition are mounted before issuing the "dd" command is a good practice.

Jessie server legacy image for PC+
Armbian_5.14_Orangepipcplus_Debian_jessie_3.4.112.raw
SHA256: CD5EB351E777651EC4F4DE71E8FD32FDECF40088A467C3C8A8A55916E1A30669   Works fine for me:    
 

Well, before using Lime2 you might want to read a bit through this thread: http://forum.armbian.com/index.php/topic/853-armbian-customization/?view=getlastpost
 
I personally use a Lime2 without problems now again but you should be warned that we had/have a couple of issues with it. If you want SATA + 2GB then the choice is easy since the CubieTruck is the only device supporting both. Apart from that: http://www.linuxatemyram.com
 
If you're adventurous then wait for the first R40 devices being ready (I still hope we see T3 on dev boards instead)

Memory is mainly used by disk cache and object storage (especially in gui apps) ... and leakage in bad software. You should check if your system needs swap (with swapon -s for example). A database may need much RAM - especially when badly designed because it then needs full table scan. A java/servlet server needs RAM to keep users context. A gui or CAD program may create numerous instance and require much memory. Apart of that, for personal usage, high memory consumption is often due to bad software (with buggy chromium, I fear that you simply cannot get enough memory). A light DB or a lignt web server dont need that much memory - especially for serving static files.
 
So buy as much of RAM that you can, but dont choose the card for the RAM unless you really know you need it : you can also use 2 cheap cards with different hardware instead of an expansive one if you have specific needs.