Your volume pot is a variable resistor to ground. The value of the pot is the maximum resistance to ground it offers the circuit when turned fully up. The higher the resistance, the more of your signal passes to the output jack. The effect of this is higher high-frequency content. Single-coil pickups are naturally brighter sounding by their design, so Stratocasters will traditionally be equipped with 250K pots to tame that brightness. Humbuckers use 500K as a normal value to increase the high end that is lost through humbucking. If you put a 250K pot resistance on a humbucking pickup, the high end content will decrease relative to a 500K pot. A quick way to test this is to "temporarily convert" your stock 500K pot to a 250K pot by clipping a 500K resistor across the inner and outer lugs of the pot. This will cause the pot and the parallel resistor's net resistance to be half the 500K value according to Ohm's Law for parallel resistors. (This is how PRS makes the 250K/500K pot switch possible on the original MEV guitar--it's on a mini switch.) See if you notice a difference. If you don't, then use the EQ pedal method or something you think works better.