Then you need to save more if you want a CPU/Motherboard upgrade (Intel). Your existing cooler will do fine on a locked chip.
'Best two' depends entirely on budget.
A Haswell i5 + motherboard will come to about $250, give the 20% or more improvement I suggested and use your existing cooler and memory.
A more modern Skylake option will give you maybe 25% better, but will cost closer to $350 because you need new memory too.
This would be a good starting place.
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor ($174.89 @ OutletPC)
Motherboard: ASRock H97 PRO4 ATX LGA1150 Motherboard ($83.89 @ OutletPC)
Total: $258.78
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-10 11:51 EST-0500
There is wiggle room when we know what you think 'best' means.