Processing power will double every 18-24 months, so your purchase will decrease in value. There is nothing you can do about it except to make sure that your system can be upgraded so that you can slow the performance disparity. RAM memory improves responsiveness of your system. Get the most hard drive space you can. Files and programs are only going to get bigger and storage space is relatively inexpensive.
Internet speed is the result of the modem and the mode of connection to the internet.
A processor upgrade will not speed-up your internet connection. The only way to get internet content faster is to get a faster connection.