You may be able to reconfigure your router to improve bandwidth.

1. Disable any Quality of Service (QoS) settings in your router setup. QoS helps police the traffic on your network letting more time-sensitive or critical traffic take priority over non-critical traffic. A common example would be VOIP (VOice over IP - Internet telephone) traffic.

Change the wireless channel to avoid interference with neighbors. Channels 1, 6 and 11 are commonly recommended as they have no overlapping frequencies. Details on changing the wireless channel setting can be found in the user manual for your router.

Dual Band Wireless-N Routers
Transmit on both 2.4GHz and 5GHz bands
100 Mbs

Requirement for streaming HD - 10 Mbps min.
Good quality 720p HD takes at least 12Mbps, and 15Mbps is a more reasonable minimum. Good quality 1080i takes at least 15Mbps, and even 28Mbps isn't enough to eliminate all artifacts (based on D-Theater tape bitrates and quality).
See:
Broadband Blog : YouTube turns on 1080p streaming

On user got better throughput by configuring an Apple Airport Express to use the 5GHz channel only.
However, 5GHz does not penetrate walls as well as 2.4GHz.

See:
Speed Test
Wireless Routers
How to improve your wireless network and boost its signal