Upgrade or Build New?

I've had my computer since July of 2009 and I'm wondering is it time for an upgrade, or is it more worth it to build a completely new PC? 

My current parts are... (never overclocked, but I guess I should have..)

Case: Antec 300 Mini Tower Gaming Case

Mobo: Gigabyte GA-MA770T-US3P ATX AM3 DDR3

Processor: AMD Phenom II X4 955 Black Edition AM3 3.2GHz 8mb cache

Graphics: XFX Radeon HD 4890 1GB 900MHz 3.9GHz GDDR5

RAM: Corsair XMS3 TW3X4G1333C9 4GB DDR3 2x2GB DDR3-133 CL 9-9-9-24 Dual Channel

PSU: Antec Earthwatts 650W ATX12V V2.2 EPS12V Active PFC 80PLUS 120mm fan

HDD: WD Caviar Black 640GB 7200RPM 32MB dual proc 3.5IN SATA 

CD Drive: Samsung SH-S223F Black 22x

I've had problems here and there with BSODs, not booting up, etc etc, but they seemed to just go away after awhile.. 

Any suggestions? or suggestions for parts to upgrade with? I'm not familiar with compatibility of parts either, so I'm no where near knowledgable to do this myself.

No need to toss systems, upgrading chunks here and there will work fine for you. Depending on how much you want to spend I'd say...

Things to replace:

  • Mobo
  • CPU
  • GPU

Things you may want to replace: 

  •  Memory

Things to add:

  • SSD

Things to keep:

  • Case
  • PSU
  • HDD
  • ODD

I don't know how high you want to upgrade, but I'd say following whats listed above would bring you up to date. The reason you might want to replace the memory is because 4GB 1333MHz mem is kinda small and slow, its really cheap to get an 8GB pair of 1600MHz or 1866MHz mem.

I would just replace the motherboard ram and GPU. Keep the CPU, seeing it is still a great CPU. Also get a CPU Cooler so you can OVERCLOCK!

I'll echo the latter half of his statement, a CPU cooler would be an important addition.

That gfx is pants i would get a 7870 and 8gb of 1866 kit just run it at 1333 and then you will have a good mid range pc again.

The cpu is fine but if you still have money to burn after the gpu and memory upgrade then get a i5-3570k and mobo and ssd

That GFX is Pants?

What does that even mean? What kind of dialect is that?

probably the google dialect....

I'm pretty sure I can't just buy whatever I see and think is "good" and just piece thigns together.. I'm in Canada and looking to buy from NCIX, or price match at ME.. 

I've been looking at the samsung 830 ssd's, and if I do upgrade, I'll get 8GB of faster ram for sure.. (does the one in the newest build video work? 1866 speed). 7870 would also be a really nice addition. What cooler should I get to OC my CPU?