My alpine 9835 and 880PRS are enroute including a PG 8v TL66 line driver.....would you guys suggest I still use an 8v line driver to both these HUs?

My RF amp reads:
Signal Voltage Adjustment Range...........variable from 150mV to 5V (RCA Input)

Would the 8v line driver damage anything on my 5V amp?

'coz if its not needed & if it may pose a problem to the amp - I could immediately sell this to some of my friends who still have 2.2v HUs.