Side Project: a Switched Attenuator

I use a PC oscilloscope for many AC measurements and for measuring distortion.  My audio interface connected via USB provides the analog inputs (2 channels).  Unfortunately, they have a maximum input of 2Volts.  I need to measure up to 500 volts.  For a while, I used a couple high wattage resistors as a voltage divider to attenuate the voltage down to 2v or less.  Sometimes I need to measure low voltages, sometimes high, and switching the resistors became a pain in the ass.  I decided to build a switched attenuator.  It's basically just a ladder divider.  Since I'm often measuring the output of the amp, I also added 8ohm thick film resistor which can be switched in to provide the speaker load without a speaker blasting out ear piercing test tones.  Here it is with one channel completed: