Without getting too technical, when you think about changing ISP you might want to bear in mind the following:
The limiting factors of the actual speed that you will be get is not limited to the distance from your house to the cabinet..So many other factors are involved such as the quality of the copper from the cabinet to your house, your internal wiring, interference, this can go on and on and on..
No matter which ISP you choose, they should be able to give you an estimated speed that your line might support before you place an order. This is not guaranteed. The actual speed
that you would receive can only be known once you have an active service.
Along with the usual checks regarding the ISP reputation, price and customer service record (because it would be nice to know they answer the phone and emails ), you should also try to find out the status of the ISPs Network. Ideally you want an ISP with an under-subscribed network to be sure you are not getting delays before you even leave the ISP out to the Internet!
As a gamer, you should also check what kind of peering agreements they have in place.
Hope that helps