Just one caution: how hard do you drive your speakers? The 300R, 12 watt resistor may get hot when used hard, in place of a 15 watt. Have you considered doubling up in parallel? I would be sure to meet or exceed all voltage and power specs, and match values of resistance or capacitance as closely as possible.
Rather than brand name, consider technology when buying caps. Film and foil is notably better than any metallized product. I like tin foil and styrene film, especially from MIT multi cap - pricey, but worth it in spades. Mills is good unless you have deep pockets.
This is backwards
Two 15ohm 12watt resistor in series will give you a 30ohm 24watt. You want to parallel resistors to increase wattage.
You can in series or parallel resistors to increase wattage!
You can parallel two 60ohm 12watt resistors to get the same result.
P= V x I
Two identical resistor in series, each resistor only see half of the voltage.
identical resistor in
each resistor only take half of the current.