Best USB / PCI WiFi Adapter for low signal network?

Hi,

I live in a shared house and our Wifi router is the bog standard low spec ISP provided type of device. The problem with this is that there are a few walls between the location of the router and my room and the signal I get is quite low. Because of a number of reasons I cannot increase the strebgth of the router signal nor move it to somewhere closer to my room. As such, the only options I've got left are to use a cable (not feasible) or a very good quality WiFi adapter on my desktop computer.

Right now I'm using the Edimax EW-7318USg USB adapter with included antena and which is supposed to be a high gain adapter. With this hardware I am getting a significantly better link then with the budget £9.99 type of adapter but still not quite good enough. The problem is that I have to stick my WiFi adapter as close to the door to my room as possible and fiddle with it a bit before I get sensible reception.

Having said all these, I was wondering if anyone could advise me on some really good high gain WiFi adapter, either USB or PCI, which could help me get a better link.

Thanks