Resistors are extremely important to your audio networks, and fortunately they often represent some of the most affordable upgrade options available.
A few dollars can get you into high-quality resistor products.
Surplus Mills 12W (15 & 30 ohm only)
Surplus Ohmite Audio Gold 10W (2.2, 3.3, 8 ohm only)
Visaton MOX resistors 10W (pending)
Ohmite Audio Gold 10W (pending)
Charcroft resistor (pending)
Additional product lines pending