A little over the $150 budget, but would still be a solid system to have.
PCPartPicker part list: http://pcpartpicker.com/p/ekr7
Price breakdown by merchant: http://pcpartpicker.com/p/ekr7/by_merchant/
CPU: AMD Phenom II X4 965 Black 3.4GHz Quad-Core Processor ($98.24 @ Amazon)
Motherboard: ASRock 960GM/U3S3 FX Micro ATX AM3+ Motherboard ($60.98 @ SuperBiiz)
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-02-14 12:12 EST-0500)