2 x Apple TV 3 units purchased late 2013 both dropping WiFi or performing terribly after sleeping

Question

Hello,
I purchased these 2 apple TV units separately.  One of them was purchased from the Apple store in July 2013 and the other in September 2013.  They operate perfectly when I used a wired connection but when I use WiFi they both drop the connection randomly and perform terribly (unusable) when coming out of sleep.  When the Apple TV's are rebooted they work well again but I shouldn't have to restart them every time I want to use them after they've been sleeping.
The WiFi AP I use is a D-Link DAP-2310.  In addition to running the AP as 802.11b/g/n I've tried to configure it as 802.11b only, 802.11b/g only and 802.11n only.  This makes no difference with the performance other than in 802.11b only it's just slow all the time of course.  While configured as 802.11b/g only I turned off WMM but this made no difference.  The network performance was absolutely terrible (unusable) after they were sleeping as usual.  AFAIK with 802.11n WMM is always on since the option is greyed out and set to "yes" when 802.11n only mode is set.
My wife's PC uses WiFi and has no problems (continuously using 802.11n).  My MacBook Air uses 802.11n continuously with no down-grade to a lower 802.11 mode and has no problems.  I've ensured my WiFi channel is not being used by any other visible SSID around my house.  I am using channel 3 and no one else is.
I heard about an Apple TV 3 replacement program and originally the serial numbers that had the problem matched my unit but apparently Apple had the positions of the letters wrong and my Apple TV's no longer qualify for this replacement program. (See https://discussions.apple.com/message/21802730#21802730 for more info on that)
Not sure what my next move should be.

Answer 1

Hi vazandrew,
Thanks for replying.  I downloaded iStumbler but it pretty much does the same thing as the WiFi diagnostics tools built into OSX (some information http://osxdaily.com/2012/07/31/wi-fi-scanner-mac-os-x-mountain-lion/). 
I used the WiFi diagnostics tools to make sure the signal was good in the rooms where the Apple TV 3 units and also made sure nothing else was using the same channel.  It's possible, although not likely because I live in a fairly rural area, that someone has a non-broadcasted SSID on the same channel as me.  I don't think that's the case though.
I did switch channels a few times over the course of 3-4 days last week but that didn't make any difference in the performance after sleep on the ATV3 units.  I also changed from 40MHz to 20Mhz channel width as well.  These changes made no difference.  The ATV3 units still had terrible and unsuable network performance until they were restarted.  A power cycle is not necessary though - just a restart. 
I've had the DLink AP for just around a year.  My previous WiFi router died so I stepped up to a Cisco RV042G and a DLink AP so if my WiFi bridge died I'd just be replacing the AP instead of a whole router.
Since the problem is with both ATV3 units its either both of them because they are similar production times *OR* the AP itself.  Since I have absolutely no problems with WiFi on my laptop or my wive's PC though that kind of leaves the ATV3 units as being misbehaving.
Maybe I'll just have to spend a few bucks on some cabling and a small switch and put wired ethernet on these suckers.