Not overkill. I prefer separates which does improve the sound quality, at the expense of higher total price and more space required for separate units. I have the Asgard 3 and Modi Multibit, which I believe would pair well with your future Sundara if I’m understanding you correctly.
There are good recommendations offered earlier in this thread.
The Sundara is a lower sensitivity planar that would benefit from an amp with a bit of power, such as the Asgard 3. Less powerful amps will sound good, but you might notice a difference in soundstage, speed, dynamics, sub bass.
Between the Modi 3, Modius, and Modi Multibit, these are all solid models and it depends on your budget, the connections of each unit, and whether you favor the sound profile of delta sigma or multibit DACs.
Here’s a recent comparison of the Asgard 3 and Jotunheim.