Tweaking Trendnet TEW-691 GR to get fast reliable internet

I've recently upgraded my WRT54G router to a Trendnet TEW-691 GR 450mps wireless N router and want to tweak it so that I get the best possible internet experience out of it but don't know a lot about doing this. I thought this thing would be faster and more reliable than the linksys but I'm having trouble with range, weak signal, signal intermittently dropping for a few seconds and Lag with some xbox games. The worst is when I'm laying in bed in the room with the tivo 25-30' away and using my iphone or xoom and the internet becomes spotty and drops intermittently. I'm looking for some advice from anyone who has a similar router or knows some proven settings that one can put into a router to get the best experience.

Here's my setup.

-Trendnet TEW-691GR set in mixed b/g/n mode hard wired to my computer transmitting on channel 8 2447Mhz (some program I downloaded and ran made it look as though this was the least congested in my city block), HT physical set to Auto 20/40 with 20/40 coexistence disabled, wpa2 security with AES. Latest firmware installed.
-Comcast Internet with DNS set to the closest one in my city
-Tivo with G adapter in room 30' away. Shows a weak signal but streams ok
-wii with G adapter i think in room 25' away. seems to work fine.
-xbox with wireless N in another room about 25' away. Feels like I get a little lag sometimes playing games but overall pretty good.
-iphone 4 and xoom devices with wireless N adapters. Get good signal on xoom pretty much everywhere but the iphone is sucking anywhere in house over wireless (might be phone)

speed test done on my computer hardwired to the router shows upload and download speeds slightly above ISP average

What I'm trying to accomplish is a more consistent reliable signal for all my devices but am not sure if there is some setting I need to tweak do this. Any help would be appreciated.