Well for CPUs there is this AMD Athlon II X3 and this other AMD Athlon II X4. Though my honest advice is save up some money and get the Phenom II X4.
As for a cheaper GPU, well, the ASUS Radeon HD 6670 1GB 128-bit GDDR5 should fare pretty well against "normal"/medium BF3 (and a reasonable resolution). The card is $85.66 after the rebate and shipping cost, but, here's a GIGABYTE GV-R667D3-1GI Radeon HD 6670 1GB 128-bit DDR3 for $55.97 after rebate and shipping cost.