The only thing you need to add is a dual monitor. No more, no less. Your hard drive is fast enough to have a few symbols open, but not for multi-hundred symbol streams. I recommend http://www.customtradingcomputers.com .
With today's technologies, the difference may not be that high. I have a D-Link wireless 300N+ router at home. And on my computers they all have USB 300N wifi adapters. From all the SpeedTest tests I made, they showed 18 Mbps most of the time. It is just about as fast as you can get with the wired DJ45 connection into the router/cable-modem. But the more devices you have at home sharing the same wifi bandwidth, each will compete with each other to for the data packets. The wired connections may be better in that case. I am far from seeing network contension so I left them at wireless.
Any 'edge' you get off having a super fast computer is irrelevant when you compare it to having a good viable trading strategy. Unless, your strategy predicates the need for high end equipment, 90% of computers will do the job. Most trading applications only use 1 CPU, AFAIK.
you can google and find the answer on this question yourself. for trading you don't need fastest. you need RELIABLE + SECURE connection.