upgrading from nvidia 8400gs for gaming

hi, i currently have a dell inspiron 570 and want to upgrade my video card once again from a nvidia 8400gs to something more powerful for gaming. my budget it 120$. i need something compatible with my motherboard, the last tech forum i asked for help on they kept giving me high powered video cards that are not compatible with my motherboard.

mother board- Dell 4GJJT AMD
cpu- AMD Athlon II X4 630(2.80GHz)
ram- 6GB
operating system- vista 64bit.
power supply- EVGA 430 W1 80+
current video card- nivida geforce 8400gs