How are you measuring your performance, via your torrent app? Regardless, that isn't too bad given you only have a 2Mbps connection.
Wireless connectivity is not as effective as wired connectivity and even with a 54Mbps system, you won't come anywhere close to getting that level of throughput. The overhead of managing the connection, error correction, re-transmits, interference, etc all play a role, as well as signal strength.
You also have the issue of a fairly underwhelming computer that must process all of the data. In your case, if it works, leave it alone.
You can check your router to make sure you don't have any caps imposed. Also, look at your torrent config and make sure you aren't capping yourself as well. Last, keep in mind that some torrent apps will cap themselves based on a ratio of upload and download speeds.