No speed improvement with A6200

Not saying it's either one, Just saying you cannot rule them out until you do some research and run some test. Is it slow due to a NAS network card setting or a NAS drive failing or is it the dell which seems unlikely seeing that it is newer with a i7. Take a large video file and copy from laptop to nas then copy back to laptop compare both times while using a wired connection see if there is a huge difference between write speeds it may point you in the write direction. Being that you expected better numbers with new wireless card and didn't get them then I would question your NAS. When I am looking to benchmark my nas I always reboot it first. Have you run a speed test using a site favored by your ISP. Most have a site they recommend, does it match what you're paying for? My A6100 has a through put around 13mbps if I remember correctly and it's a USB 2 device connecting at 290Mbps Good Luck!