New Computer--Poor Wi-Fi Performance--I'm Exhausted

I bought a brand new Acer G3620 with a 3rd Gen i7 and received it last week. The first thing I did was a clean install of Windows 7 Ultimate. I have been unable to get decent wifi service on the PC. I've installed all of the drivers from Acer's website and all updates to Windows 7.

My SpeedTests have averaged about 2-3 Mbps. All other wireless devices in the house average 30-35. The ping seems to be normal.

I tried to disable wireless security but it didn't help. I have reset all of the router's settings to no avail.

I bought a new ASUS PCE-N10 PCIe wifi card and there has been no difference in performance. I tried installing the wifi cards into a different PCIe port.

I also tried using the Linksys E2000 router I have instead of the Qwest provided router by setting up transparent bridging--and no difference.

When I plugged in a very cheap USB dongle, I was able to get about 15Mbps on speedtest--but inconsistently!

I'm thinking the problem is software based--but aside from changing security settings and attempting to use different drivers, I am completely out of ideas...

Help! I need somebody!