BleepingComputer.com: Looking for upgrade suggestions

Hey all, just looking for suggestions on what I should upgrade on my 3 year old gaming desktop. Here's the specs:

Windows 7 x64
Gigabyte GA-MA770T-UD3P
AMD Phenom II x2 550 BE
ATI Radeon HD 4850 1GB
2x2GB DDR3 G.Skill RAM
EarthWatts 500W PSU
I think my case is an old Sonata III or something similar.

I can actually run most new games like BF3 and Skyrim on relatively high settings (usually with AA off or low, though). I'm not entirely sure what my weakest component is right now, my CPU or GPU. I'm looking to spend ~$150 to upgrade one of those, most likely.
I just saw this FX-6100 http://www.newegg.com/Product/Product.aspx?Item=N82E16819103962 but I don't know anything about them or if it might better to get a Phenom X4 or something instead. Edit: Just realized the FX series is AM3+ so I couldn't put it in this mobo. Still curious about it in general though.

Also I just realized my mobo is pretty old now since they've got like 900 series out there...though not sure if it's necessary to upgrade that since it has AM3 socket still.

This post has been edited by mb9023: 10 February 2012 - 05:12 PM

For gaming, you would want a quad core cpu like this. If your willing to spend more then one upgrade, then the graphics card would be next and power supply.

How about the 975? Or there is a 980 OEM on there also for $160. Would it be safe to use my current stock heatsink/fan with that? I'm assuming the 125W up from my current 80W processor mainly just means it will get hotter, correct?

The 975 is just higher clocked by 600mhz. Yes, it should be safe to use your current cpu fan. Yes it will get hotter and consume more power.

I think I might grab the 980 since it stocks at 3.7GHz. I'll have to watch my temps though...I can grab an aftermarket cooler if it ends up being too hot. I appreciate your input.

You can probably easily push it to 4GHz with a aftermarket cooler.

First Upgrade the power supply to a Corsair 750w 12v Single rail Unit, Then add to to 8GB Ram. Last upgrade the ATi Card to something newer that your system can handle.

You don't really need to upgrade your PSU unless you are upgrading to an AMD Radeon 6900 or 7900 system. Corsair is good, but you don't really need to update unless you get a higher end GPU. You also don't need 8GB unless you keep tons of windows open as most programs are not native 64-bit and, thus, cannot use more than 4GB at any one time.

750W is just a bit too much, as a solid 600W power supply would do if the OP does choose to upgrade to the 6900 or 7900 series graphics card. 4GB of ram is plenty for most games.