I currently have a computer I put together when I was 14. I'd like to upgrade it, keeping whatever parts I should keep, and replacing what ever else is needed, to make it better suited for more types of gaming. I'm also looking to build it in a Haf XB case, is that a smart idea? Anyway, Here are my current specs:
Graphics Card: GeForce GTX 550 Ti
Motherboard: Biostar a880g+
Processor: AMD Phenom(tm) II X6 1055T Processor 2.80 GHz
Hard Drive: WD Caviar Green, 2tb
Ram: 8 gb DDR3 (4 gb X 2)
If someone could help by guiding me through an upgraded build for my PC, that would be great. Current budget is $400, and I'd like to keep it there if at all possible. Thanks in advance!
$400 is quite a small amount of money to have to spend, especially when a HAF XB costs ~ $90.
As for the case, its an unusual orientation which has its benefits. As you can see from this picture - http://archive.benchmarkreviews.com/images/reviews/case...
Its going to have issues with footprint (be it floorspace or deskspace), but if that's what you want there isn't really a reason not to, its a good case. The main negative is that with a small budget, $90 on a case is going to kill your performance. Reusing your current case is maybe the way to go.
With regards to your current components, there are a few issues.
The HDD is not ideal, Caviar Green is low power/efficiency, not speed. Upgrading to a faster HDD or an SSD will improve your overall experience, but it's not going to give you a substantial gaming boost.
There are CPU upgrades available for that motherboard, in the form of X4 Phenom Black variants (965+) but availability isn't great, and the performance boost from spending $100 isn't going to be huge.
The obvious choice for an upgrade is the graphics card. You don't mention your PSU, so you might be limited in that aspect, but spending a good amount of your budget here is likely to give you a good return on your investment. As an example, newegg are doing a 7870XT for $140 after rebates, which is fantastic value/performance.
Basically, your motherboard is a bit of a dead end, which is going to limit you. My advice would be to spend under half your budget on graphics (and anything else you need, be it PSU/case etc), and save the rest for when you can afford to upgrade the platform.
If you try to build a new system from scratch for $400, you aren't going to get anything that's dramatically better than your current setup.