Yes, the usage of third party fan&heatsink void the Intel warranty on your processor. The Intel fan is made to keep the Intel processor working correctly. When we run the processor without the original fan means we are running the system out of the specifications and it may damage the processor. In regards your second question, bear in mind the memory controller is embedded on the processor and the memory specifications are determined by the CPU. In this case the i5-2500 supports memory up to 1333Mhz and with a memory voltage of 1.5V (this is highly recommend). Keep the memory under those numbers for a stable system.