not sure about the nic itself but its the connection the nic is connected to that is way more important. the nic can be great but if you have a horrible ISP or bandwidth the nic isnt gonna help. most regular 10/100 nics will provide plenty of bandwidth for most needs.
This from a guy with 20 years experience

fcmartin, check out
THIS THREAD. Skuzzy and a few other discuss killer nic type cards. For the most part, they are a scam and really don't help much with your connection. The best thing YOU can do is to clean up your computer as best you can.... cut back on the processes running, run spyware cleaners, virus cleaners, and defrag. As long as your computer is "tuned up" as well as you can keep it, its the best your going to get. After that, its up to the ISP and there routing systems. Get PingPlotter. Its a free program you can use to check your connection to the HTC servers. If you have a bad connection, it will show there. Post a screen shot if you want a few opinions on how it looks.