If it's close by then it's strange you don't get 150mbps which is normal for wireless n.
However, if you are close enough to can link wired then if it was me I would swap the wireless card for an Ethernet Lan card so you have two LAN ports, as you'll get better performance than wireless - cheaper too as you can get them for around £10-20 depending on the slot type. Just make sure you get PCI or PCIe depending on the slot you are installing it into.
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