Better Antenna or New Adapter?

Well, everything has been working fine with my wireless N network until now. I have a Trendnet TEW-633GR Wireless N Gaming router, and an Encore Electronics wireless N PCI adapter. However, now my speeds are VERY inconsistent. For instance, I have a Battlefield 2 dedicated server hosted on my home server, which is on a wired connection to the router, and I have my main gaming computer which is on the wireless. Every single stinking minute of the game I am getting Connection Problem popups or whatever, the whole game will freeze (as in network freeze, or lag spike), then it goes back to normal after that second. Some other times my wireless will completely drop out, and I will get disconnected from the server. This is all LAN side, which to me is ridiculous for my wireless to be THAT inconsistent. Web surfing isn't noticeable with this kind of problem, because HTTP altogether is completely different than gaming.

So, I've decided: either get a better antenna for my adapter, or get a whole new adapter altogether (I can't get a better antenna for my router because they aren't detachable). Any ideas or suggestions on what I should do?

Thanks in advance.

P.S. - Here are links to the various things that I have or have looked at.
Router - http://www.newegg.com/Product/Prod [...] 6833156226
Adapter - http://www.newegg.com/Product/Prod [...] 6833180052
Possible new antenna - http://www.newegg.com/Product/Prod [...] 6833996013

I have tried all of those. The router is on top of a very large computer desk (at least 6 foot tall). There are no other Wifi networks other than mine, but I tried changing the channel, and I still get the same problem.

According to my adapter's software, it says that the Link Quality is at 100%, and the three Signal Strengths are near 70-80%, and the Noise Strength is at 26%. Also, when I look at my network, the software says that the connection quality is at 76%, and the dBm is at -60, or 60, not sure what the hyphen means. One thing I have noticed is that the second Signal Strength will stay at around 90%, but then drop down to 65% for a second, then go back up again. Could this mean I have poor signal strength?

I would prefer to get a better antenna, but if I need to, I will resort to getting a whole new adapter. I need to make sure that the D-Link antenna I posted originally will work with my adapter. I'm pretty sure the connector types are the same, but I just need to see about the compatibility.

I re-enabled UPnP (originally disabled) and I had no immediate improvements. I hosted a Battlefield 2 server on my home server and tested it again, and I am still getting the very frequent lag spikes.

My router had no options for disabling Port Scan and DoS.