Really slow download speeds on my new computer

I just finished building my first gaming pc. Everything is glorious except my download speeds. I have to use a wireless card (opposite end of the house from the router). My connection is good. My link speed is listed as 54mb/s in task manager (the same as my laptop in the same room), but I'm getting download speeds that range from 300kb/s to 50kb/s.

My laptop, sitting on the desk next to it, can easily get up to 10mb/s.

This is my wireless card: Esky® PCI Express Pci-e 11n 802.11b/g/n 300mbps 300m Wifi Wireless Card Adapter

Please help! (And thank you so much in advance) -Feydor