Windows PC into a Fosi V3: is an external DAC worth it?
Bus power is not the obstacle — 2.5 W asked against 4.5 W available. The speaker decides the answer: a 94.5 dB horn reproduces the same hiss 9.5 dB louder than an 85 dB monitor.
Sometimes — and with 94.5 dB horns, more often than with ordinary speakers.
Bus power is not the obstacle: the Modi+ asks for 2.5 W and the PC's USB-A port supplies 4.5 W, so nothing here needs an external supply. The reason to take the signal out of the computer digitally is the noise floor, and the speaker decides how much that matters.
Sensitivity multiplies noise, not just music. The Klipsch RP-600M II is 9.5 dB more sensitive than the KEF LS50 Meta, so at the same amplifier setting whatever hiss arrives at the input comes out 9.5 dB louder. Horn tweeters do not reveal bad sources by magic — they are simply 8.9 times more efficient at turning the same noise into sound. This is why the same onboard output that sounded clean on a previous pair of speakers becomes audible the week the Klipsch arrive.
What a DAC will not fix: the room, level matching, and hum that comes from somewhere other than the audio path.
Test before you buy. Play silence at your usual volume setting and walk up to the tweeter. If you hear nothing at 30 cm, the DAC will change nothing at 2.5 m. If you hear hiss from the seat, it is worth the money.