Why would you want to waste your money on the 2100? Bigfoot advertises that prioritizing packet preference will improve your ping by some dramatic amount. The so-called slow updates they talk about cannot be controlled by the client side. You cannot magically make a server send you packets faster. As long as you don't have a defective NIC/Modem/Cat 6/5e cable, you are sending out packets to the server as fast as possible. Bigfoot/Killer/Visiontek run adverts without showing any actual side-by-side statistical data. User reviews will attest to the lack of improvement after holding out huge hopes for this NIC. If you want to get a decent add-in NIC, Intel makes a solid product.

This is a review from Bit-Tech that will hopefully ease your mind:

Bit-Tech review of Bigfoot 2100 <---Click

Performance aside, the reason it is sold out is because it has been discontinued. Bigfoot likely has newer models for their NICs, but I would suggest going with a dedicated Intel NIC if you don't want to use onboard, but for most applications it's more than adequate. The Killer NIC cards are ridiculously overpriced and performance is questionable.

The focus for these cards is that they are "fully buffered" which essentially means that they have an integrated processor that sends and retrieves data from the system bus, reducing the demand on the CPU. But truth be told, most systems are so fast now that network card buffering is such a low demand on the CPU that the gain by using these expensive cards is marginal.

When your LAN card is using 1% (or less) of your CPU time, is it worth a hundred bucks to free up that 1%?

As Razear said, get the Intel NIC. Also try these tweaks below...

http://betanews.com/2011/01/20/use-hidden-windows-tweaks-to-speed-up-your-internet-and-network-connections/

"Click "Start," type CMD, right-click the cmd.exe link and select "Run as administrator" to launch an elevated command prompt, then type:

netsh int tcp show global

-- and press "Enter" to view your system's current settings.

Then print this out, take a screen grab, or otherwise note the settings -- you're probably going to change them, and it'll be useful to have a record of the original values just in case you want to undo your tweaks later."

While in CMD as admin type in these commands below. Reboot after changes. Test your internet connection at http://www.speedtest.net/
Try out your games now, enjoy! If you run into problems (like ecn) you can reset their values, such as changing the enabled to disabled or whatever was printed out before the change. These tweaks help with hit register in games like BF3, this I'll assume is the kind of thing you are looking to improve on.

Command list:
netsh int tcp set global chimney=enabled
netsh int tcp set global dca=enabled
netsh int tcp set global netdma=enabled
netsh int tcp set global autotuninglevel=highlyrestricted
netsh int tcp set global congestionprovider=ctcp
netsh int tcp set global ecncapability=enabled

I was always curious about the killer NIC's. They just price themselves so high that it "must" be good, but I've never seen any real evidence of that. The only thing that ever caught my attention was the ability to technically increase your ping, therefore causing server side glitches and such. I made a lot of money back in the Ultima Online days using in game glitches, so it probably could have paid itself off back then.