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.