What should I replace first?

[jinscho]

First and foremost, my build is outdated and "just replace everything" is not the answer I'm currently looking for.  I use the computer mostly for work (email, web-based applications, minor photo editing) and from time to time I enjoy some casual gaming (HotS, SC2, Half-Life 2, Portal, and TF2 mostly).  I'm on a fairly limited budget, and I'm not opposed to purchasing pre-owned parts if it helps me to stretch that budget.  I'm also not opposed to using AMD cpu's but I am biased when it comes to gpu's and prefer nvidia based platforms.

 

My budget right now is $150-$200 and my choices are either to purchase a new GPU.. OR.. to upgrade my motherboard/cpu/ram.  The entire build will eventually be upgraded, I just can't decide where to start and can't do all of it at once.

 

Current build:

 

EVGA nForce 750i SLI motherboard (non-ftw edition - http://www.newegg.com/Product/Product.aspx?Item=N82E16813188033

Intel Core 2 Quad Q6600 (stock speeds - Zalman CNPS5X cooler)

8GB Corsair XMS2 DDR2-6400 (4x 2GB)

EVGA GeForce GTX 550 ti

ADATA SP600 128GB SSD boot drive

Seagate Barracuda 1 TB HDD mass storage

Corsair CX430 v2 PSU

NZXT H230 case

 

Thanks in advance for the guidance.

[GDRRiley]

get a better cooler and then save for a new GPU

[Julius159]

Buy gpu first you cpu decent

[jinscho]

Has the Q6600 really survived that well even paired with DDR2? Im currently running it at stock speeds as I'm a novice over clocker at best (had it at 2.8Ghz with good temps but dealt with intermittent memory based BSoDs and gave up on it) and haven't really spent a lot of time trying.

As for GPU any suggestions in that price range? I've found a few pre owned GTX 650 TI boosts that are well below my budget but the 960 is sitting pretty at the top end of said budget.. Too many choices that are easily better than the 550 ti