I'm not a gamer but I will voice my opinion. First of all, I don't see that combination as an overpowering rig but I do see some good and some questionable things if I were buying it. First off, is the price, I think it is too high if I were buying it and I can easily see where one could shave off a few hundred bucks by doing a self-build; however, it is understandable that one must pay for someone else to build it for them. So, here's what I like and don't like:
Hello EchoX860, Here are my thoughts as a PC gamer:
The Pros: This system is great if all you are playing is Minecraft/Warcraft. The Six-Core CPU and 16GB of RAM is a great combination for minecraft since it is CPU/RAM intensive due to the engine being based on Java. the GT 640 doesn't use a 6-pin but rather the slot itself which powers the card so it won't run too hot with only less than 100W of power which means a quiet fan, Performance is great as well. The 1TB 7200rpm has good speeds for OS/Gaming, I have a 1TB myself.
The Cons: the 450W PSU is perfectly fine but going to be honest here, the Power supply is from a brand I've never heard of and it isn't even Bronze 80+ which is highly recommend if not required for most gaming rigs. I suggest you get a PSU like the Corsair CX430 which is 80+ Bronze and is sufficient for your setup, up to you though. Another thing I dislike is that there is no Exhaust fan, it is essential to have a front to back airflow current in your PC as it will help to exhaust hot air from the cpu and gpu and keep cool air coming in. You can pick up a Coolermaster 120mm fan for a few dollars or if you want LED's a Rosewill or Coolermaster Sickleflow come in a blue LED and will get the job done, once again, up to you.
As for the rest of your rig, It looks great to me and your performance should suit your needs. Keep in mind to do a PSU upgrade, if you don't have the experience or someone to help you, the PSU that comes with the PC will run fine.
I can't help but wonder what PSU he has..It just says 450W
By the way Avatar sells it for about 650$ on their website with a GTX640.
And I think it's better if you go for AMD go for AMD on both CPU and GPU I think it's better that way.