Help me choose my GFX card!

What do you want to use this GFX card for?
How much is your budget?
What are your current full system specs?

none of those cards would be a match for the 9800gt. However, if you want to get a hd6670, the get the DDR5 version since it has much higher memory bandwidth.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

AMD HD 6670 is the best choice-
Check this Best GPU under $100

http://dgbtech.blogspot.in/2012/07/best-graphics-card-u...

Budget of around 70 and use it for mild gaming (DotA 2, TF2, CS:GO)
Specs:
According to CPU-Z, my processor is AMD Athlon II X2 255
RAM: DDR3 4GB
Mainboard = Motherboard? : Manufacturer: ASUSTek Computer INC.
Model: M4N68T-M-V2 Rev: X.0x
Chipset: Nvidia Geforece 7025 Rev: A3
Southbridge: Nvidia nForce 630a Rev: A2
LPCIO: ITE IT8721
Bios: American Megatrends Inc.
Version: 0501
Date: 08/03/10
Graphic Interface: PCI-Express
Link Width: x16 Max Supported x16
4GB DDR3

Most important information is wattage of your PSU. You might need to open your case for this.

The HD6670 is the best but you should rather go one better to get some more life out of it. HD7750 is a great card that runs on very little power.

I just bought this to run the 9800 Gt but that didn't go so well so I'm going to be using it for a AMD instead :
Antec VP-450 450W ATX 12V v2.3 Power Supply
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Ok considering you have a decent PSU.

Get this or one better HD6770 if you have some more cash.

http://www.amazon.com/EAH6670-DIS-1GD5-Radeon-GDDR5/dp/...

Holy cow that thing is massive, don't think it'll fit in my case!

Are you using a normal case or something from Acer or HP or any other type of case? Can you paste a photo. The card is standard length. It is just abit broad, but that is rarely an issue.

This is the case I have http://www.amazon.com/CyberpowerPC-GUA260-FX-6100-HD645...

It will fit no problem.

Oh good god that card will fit in that case with no problem at all you could fit a card quite a bit bigger in that case.