Hey there
Daelon DuLac: I have just come across your thread and decided to give you some insight to gaming PC, even if you have already bought that one.
CPU (Central Processing Unit): The FX 4300 is fairly old now compared to the newer FX series, you are better off getting the FX-8350. It's an Octo-core CPU clocked at 4.0 Ghz and is compatible with the same socket that the 4300 is, (AM3+).
http://www.newegg.com/Product/Product.aspx?Item=N82E16819113284&cm_re=fx_8350-_-19-113-284-_-Product
PSU (Power Supply Unit): Having a good PSU will be recommended if you plan on having multiple GPU (Graphic Processing Units) in Crossfire form, and the NVidia equivalent. Crossfire basically means that you can use multiple GPUs in the PCIe3 x 16 slots and have upwards of 8 Gig of VRAM (Video Random Access Memory). I recommend a 750 at lowest with Gold rating certified.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182073: I myself use this one, and it is a great PSU.
Ram: usually, the more RAM, the better, especially if you are using a 32 or 64 Bit OS. I wouldn't go more than 16 Gigs though, and depending on the Motherboard, you'll need to know what type you'll need.
Motherboard: It only has one PCIe x16 slot, so you'll need a new MoBo if you want multiple GPU's.
GPU: That GPU is very dated, so will not Run Skyrim well at all with just 1 Gig of dedicated VRAM. Most games now a-days require more that one, usually 2, so I suggest getting an AMD Radeon 7850 which is far more powerful than the 6450. If possible, either get the 7870, or 7900 series. If you have extra money to spend, I would recommend the NVidia Gtx 770 Super Clocked Edition which is near the best card on the market at the moment.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130921&cm_re=GTX_770-_-14-130-921-_-Product
Case: The case is Ok, but you'll want a full tower for multiple GPU's.
For a few hundred more, you can have a system twice as powerful as that one, and last a fairly good time, longer than the current (Next) Gen systems that is.