It would help if you gave us details about your wifi setup, and what kind of media you are streaming (resolution, bitrate, etc). But basically, you wont be able to stream most 1080 material over a 54g network, it's too slow.
Hardline it. Wireless is simply never going to work 100% of the time for 1080p (unless it's super compressed 1080p I suppose). You could too Plex Media Center to transcode it to a lower quality, which would help.
I am successfuly playing Bluray ISOs over my network with a Netgear R6300 and a Netgear A6200 (80211.ac) with file sharing. I am using Virtual Clone Drive and PowerDVD10 ultra or XBMC. I just tried and eperiment I played two different movies at the same time over the wireless network one is stored on one computer and one is stored on the other. They both play just fine.
CPU - Sandy Bridge LGA1155 (3D) Intel i3-2100
MoBo - GIGABYTE GA-Z68MA
RAM - G.Skill 2x2GB DDR3
HDD - WD Green 2TB
CPU - Intel® Core i7-3632QM
RAM - 8GB DDR3
Router is just the standard Cable Modem with a built in wireless router from Verizon Fios. I do know its a newer version capable of 300 Mbps over the wireless. (Model: Actiontec mi424wr)
Here's the thing. I play all my movies through my HTPC on my 1080 HDTV, or stream them to my roku located in my bedroom that is connected to a 720 HDTV via Plex. I just got a new laptop that is 1080p and for shits and giggles I was trying to stream Blu-Rays from my HTPC to the laptop via Plex so I could see how they looked. I know I could always just directly hard wire my laptop to the router but that's beside the point. From what I'm gathering streaming 1080p over wireless isn't practical.