What kind of PSU do you have, and does it have 2 PCI-E connectors?
Also how hard a limit is the $150?
The R9 270 / 280 series are really just rebranded Radeon 78xx and 79xx cards. Newegg has some of the original 7xxx series cards new, decent prices. This is assuming your PSU can handle it.
MINIMUM REQUIREMENTS:
OS: Windows 7 64-bit
INTEL CPU: Core 2 Duo E6600
AMD CPU: Athlon 64 X2 6400
SYSTEM RAM: 4GB
NVIDIA VIDEO CARD: GeForce GTX 560
ATI VIDEO CARD: Radeon HD 5770
VIDEO MEMORY: 1GB
HARD DRIVE: 50GB
RECOMMENDED REQUIREMENTS:
OS: Windows 7 64-bit
INTEL CPU: Core i7-920
AMD CPU: A8-3870K
SYSTEM RAM: 6GB
NVIDIA VIDEO CARD: GeForce GTX 670 or GTX 760
ATI VIDEO CARD: Radeon R9 280
VIDEO MEMORY: 2GB
HARD DRIVE: 50GB
7950 for $134 no rebate (R9 280):
http://www.newegg.com/Product/Produc...82E16814161400
7870 for $114 no rebate (R9 270) :
http://www.newegg.com/Product/Produc...82E16814161410