Bosch laser measure, inexpensive model. You can check the exact distance between you and the two speakers, and you don't need someone to hold the other end of the tape measure.
Speaker Positioning
I know from speaker position is critical in achieving the best results from a given system. Is there a dynamic way to measure placement of each speaker to make certain they are the exact same distances from back/side wall, cabinets, seating, etc. beyond a measuring tape and listening to the results? Seems to me if minor differences pay large returns, you could be tinkering with this a long time. Thanks for the indulgence.