The RF7 -III can handle 250 wpc and 1000 watts peak , which means the 120 wpc HK 3770 although capable to power these speakers will distort much earlier than if we take as an example a 240wpc amplifier for a comparison -
so , how will it sound ? a 240 wpc amplifier will give you 3db more presence (SPL ) than your current HK 3770 -120wpc amplifier because we are at 2x the power output for an equal sound level -
the improvement of a 2x more powerful amplifier = +3db = more headroom = 2x less distortion = cleaner sound -