We used PerformanceTest 6.1 by PassMark which you can find out more information about here. It has a handy Advanced Networking section which is perfect for our testing.
Doing our best to emulate a real-world performance scenario, I setup a server running Windows 2008 R2 (x64) Server (2x Xeon Quad Core 3.0 GHz 1333MHz FSB, 4GB DDR2 FB-DIMMS, 2x 146GB SAS drives in RAID 1) and the client PC was an MSI Wind 200 with built-in Intel 802.11n (Intel WiFi Link 5100 AGN) adapter.
The results were gathered by sending data from the MSI netbook to the server at different distances with the built in adapter, a TPLink TL-WN821N, and then a TRENDNet TEW-664UB adapter for both 2.4GHz and 5GHz speeds. Average transmission speeds were recorded for each.
The connections speeds for the 2.4GHz channel varied between 52Kbps and 144Kbps. The lower speeds were during periods of low network traffic, so that did not bother us too much. For the 5GHz channel we saw speeds of 270Kbps to 300Kbps. It was quite a shock to see this after the lower speed 2.4GHz.
The performance was not where we thought it would be, although the short range performance was outstanding and generally faster than the other routers we have tested. When we left line-of-site things slowed down a little. We were able to compensate for some of that by using the 5GHz channel and also with some channel tuning. But I would have liked to see things running a little faster.
Gaming performance was good, especially with the Gaming QoS on. Our ping times without the QoS were in the mid-60s for a busy game server. When we kicked the Easy QoS on we saw them drop into the 40s. Now, it is important to remember that your results here may vary depending on your network speed and also the distance to the server in question. With that said, the ASUS RT-N56U will not be the piece that holds you back.
The multi-media experience over the 2.4GHz band was a little rough, but that was because in the area around my house there are over 10 wireless access points running 2.4GHz. Even though I run a different channel and secondary channel, their signal interferes with mine. This caused a few stutters when the audio (from the HD MKV file) got a little complex.
Once we kicked over to the relatively clean 5GHz channel, this was removed and things cleared up. We had no issues with Netflix, Hulu or with pulling HD video over the wireless network. It seems that the 5GHz range is certainly the way to go for your home entertainment systems.