Four spatial streams is 4x the speed of a single spatial stream. 802.11n allowed for 1, 2, 3, or 4 spatial streams (this is closely related to the 'MIMO' numbers like 1x1, 2x2, etc.).
The main options were how many 'spatial streams' your hardware would support, and how wide of channels your hardware would support. The 802.11n standard allowed for a wide range of hardware with different capabilities. Short answer: Make sure your AP (wireless router) is set to use 40MHz-wide channels, and perhaps try some other 5GHz channels instead of 132, in case your client is choking on 132 and accidentally treating it like a 20MHz-wide channel.
