Looking at specs for Empyrean, 32ohm, 100 dB at 1mW, fairly sensitive. EX5 on high gain max out over 1 watt at 32 ohm, which translates to 130 dB SPL, so at reasonable volume there should be plenty of headroom for peaks.
Haven't found sensitivity figure for Twin Pulse
My recommendation is for EX5, digital volume control eliminates potential channel imbalance of analog pot