Klipsch RP-600M II on a Fosi V3: are 45 watts enough?
45 W land 1.9 dB under the 105 dB reference peak, and normal listening takes 0.70 W. The same amplifier on a KEF LS50 Meta manages 93.6 dB — a 9.5 dB gap that no amplifier budget closes.
Yes — 45 W land 1.9 dB under the 105 dB reference peak, and the first watt does most of the work.
At 94.5 dB/W/m and 2.5 m, the Fosi's 45 W into 8 Ω give 103.1 dB at the seat. A normal 85 dB listening level asks for 0.70 W. The 4.4 Ω minimum dip sits comfortably inside the Fosi's 2 Ω rating, and 45 W falls between Klipsch's recommended 25 and 100 W continuous.
The comparison is the number worth keeping. The same amplifier on the KEF LS50 Meta manages 93.6 dB. The difference is 9.5 dB — purely the speakers' sensitivity — and 9.5 dB is 8.9 times the power. To make the LS50 Meta as loud as this Klipsch you would need roughly 400 W. Sensitivity buys more level than any amplifier upgrade available at this price.
If you want the last 1.9 dB. An 80 W receiver such as the RX-V4A adds 2.5 dB and gets you just past reference. That is the entire difference, and it comes with a caveat: a horn tweeter at 94.5 dB will let you hear the receiver's noise floor at the same time.