The Reason I Think I am Stress

I NEED TO UPGRADE MY COMPUTER!
ARGGGG!!!!

It's been getting more and more slower.
As well as..... laggish..
Not that much so I can still take it for normal use but not when it starts jamming and I have to start waiting for it to recover or just restart it.

What's more pathetic?
I am not a hardcore gamer...
More of a in-between causal and hardcore type. (Semi-hardcore?)
And I had to UNDERCLOCK my computer, which also includes the GFX just to make sure it does not die on me during normal use and gaming.
Oh, and it's not driver problem cause I had already updated it to the newest one that was released on Jan2011.
It is also partly due to the pathetic 9600GT.

In case you do not know the problem with it, 9600GT is just 8800 power up w/o solving its initial problems like the TEMPERATURE, put a new name and poof - new product, come and buy it!
A sad fact that I only found out months later after I bought it.
It's also partly due to my budget casing which only cost me $30.
Time to change that too!

Thank to that, I can hardly play anything at all since some of my games like Fallout: New Vegas would crash at some random point.
Just by loading a new turn in Civ5 can lag to boredom too.
Not to mention running my Python program can also cause it to hang or freeze up sometimes but it will let off after I don't known how long.

Need to look into more parts info before I make my move!
Budget around 1.4k which can fetch me a decent 1.
Well, problem is...
I don't research hardware stuff that much!!!
>.<