There are many tennis stores that would allow you to demo racquets. Also, if you have a close friend, you can ask if you can exchange racquets for a day or two. This is how I changed my old racquet to the Babolat Pure Drive.
do not buy racquets off ebay. they are often fakes, looking identical, but playing like rubbish. amazon is safer if you have to buy online. Alternatively you could go to your local tennis club. they usually sell tennis racquets as well.
The number on the Wilson racquets refers to a stiffness index rating. Racquets in the range of 1-3 are stiff and powerful racquets designed for people with compact strokes. 4-5 are designed for a balance between power and control for players with med...