i have a bmw k1200lt the speakers have dry rot i am replacing the 4 ohm 60 watt speakers with 8 ohm 120 watt(pioneer i think) speakers. The bikes amp has 4 X 30 watt output.

I have heard that the amp is very sensitive to changes in the ohms of the speakers could i  add a 8 ohm 40 watt resister and be ok in parallel that is?

if so is there any place any one would recommend to buy resisters from?