Wireless/Wired Networking

I have a 30 mbps down / 25 up connection.
However, I only get around 20 down and 18-19 up, when connected wirelessly (Actiontec wireless-g router supplied by Verizon).
On the computer with a wired connection, I almost always get something close to 30/25 on speed tests.

Also, I disconnect randomly every once in a while. I'm not sure if it's the built-in adapter, or the router itself. I can't have that happening, because I run programs that need to be connected to the internet 24/7.

My room is 1 floor above the router, and my parents don't want cables running across the hallway and up the stairs.

I don't think I can just replace the router with an N router, because the one supplied is required for certain TV functions.

I don't know what to do.