195 is already the minimum width recommended by Honda for your tires. You also have a 205/60R15 performance option recommended by Honda (probably standard on the Si models).
You can always go narrower with a 185/70R15 but then you will be registering 0.9% too slow (i.e. 100kph on the speedometer would actually be 105kph on a radar gun...)
The debate of narrower vs wider depends on typical driving conditions. In the winter, if the streets are often unplowed and you need to cut through it, narrower is best to apply more weight on a smaller surface area. However, if the streets are plowed quickly to pavement and roads are heavily salted, more surface area for grip should win out.
In your case, I'd stick with 195/65R15 for the winter and get a nice pair of 205/60R15's (or 205/55R16) for the summer
Of course, before going off sizes, take into consideration wheel well clearances and whether or not you will need new rims to accommodate the size.
