Doubling the power only results in a 3db increase in loudness = 1.25 or 25% increase.
This should be completely manageable.
Peak available power is irrelevant in this context. We are typically listening to primarily the firsts watt of power. Peak power is rarely called upon, but the extra headroom can be of benefit when you have a difficult load or are playing the music loud.
All preamps allow the volume to be reduced to zero in any event.
Definitely not overkill. It isn’t the power that matters. When sound quality is at stake go for the best. M700 s if you can’t go BHK.
Hi! I’m getting my S300 today! Really excited about it, will be powered my my Accuphase e-280 to drive Kudos C10. I also use a Holo Spring KTE R2R DAC and a REL 7/x.
I will connect the S300 using high quality RCA from preout (only available option unless I use a custom RCA to XLR cable ?).
The REL will be added as mentioned “So, final, successful wiring configuration: Yellow to Left (+), Red to Right (+), and Black to chassis ground.”
Then when operating will be turned on as follows
Accuphase Preamp > PS 300
Turn off
PS300 (just stand by mode) > Accuphase Preamp
Keep volume down all time when turning off
Will test leaving the REL as it is on see if no hum happens.
Burn 
it 100 hrs
Any newbie advice will be appreciated! Thanks
BTW S300 will be placed at the bottom of the rack.
Why I got it? The Kudos C10 can take 20-200w, when I saw them playing they were connected with a Naim and m700, they sounded very good. Using the Accuphase e-280 was fine but base seemed a bit slow, so I upgraded to what I could get. I’m also fine tuning with Audiolense xo at the end.
For the REL I will do this method instead, because I’ve it already working on the Accuphase without any issues so will be like bi-amping speakers:
Welcome aboard! Nice setup. It will be interesting to know your thoughts on the S300 vs E280. It may sound better but nothing will look better making music than an Accuphase amp.
Hi! Thanks so much for your comments!
I previously owned a pair of ProAc DB1. They sounded great in the low and midrange, but the lower frequencies lacked detail. One day, while visiting an audio shop that was closing down to pick up a power bar, I got curious about the Kudos C10. After listening to them driven by a Naim and a PS Audio M700, I was completely hooked. They sounded fantastic, and since the discounted price was close to what I could get for my DB1, I decided to sell them and bring home the C10s (the full price would’ve been beyond my reach 
).
Once set up with my Accuphase E‑280, most music sounded excellent, but I felt the low end was a bit slow or boomy. I used Audiolense XO to create a convolution filter, which helped tighten things up, though it required more power and slightly reduced some layering in the sound.
A couple of months later, I was lucky to find a last‑unit deal on a PS Audio S300 and noticed it also had a solid review on ASR. I decided to upgrade, and it turned out to be the perfect match — tighter, faster bass combined with the smooth AAVA volume control of the Accuphase. I might do a subtle room correction again, but for now, I’m really happy with the overall sound.
Further testing: The Accuphase sounds really good as well in what is details and layers with in music, After testing same music, I find the S300 fills some gaps where the Accuphase lacked energy to drive the midrange in some deep bass songs, where the the S300 made it tighter and faster. Both complement each other well!
That’s a fantastic point about the UMIK-1/REW setup!
I know the thread is specifically about SPL meters, but for anyone who wants to go beyond simple volume checks and get into deeper room calibration, that calibrated microphone with Room EQ Wizard is seriously hard to beat for the price. Definitely the most useful takeaway here!