Do the foam mod first as it is the easiest.
Just drop in, and reversible.
The tape mod reduces reflection and increases clarity,
While the foam mod delivers impact and extension and trebles refinement.
Just do it.
I'm very surprised that you find the HEK lacking impact/punchiness. From what I remember about reading your other posts, you're not using stock cables, correct?
I'm using the Stratus to drive the HEK and I find that the HEK sometimes has too much impact/punchiness to the point where mid-range seems slightly shelved/recessed. This is sort of irrelevant, considering I am using completely different upstream equipment as well as a different tube combination.
What level of volume do you listen at with the Stratus?
I do have upgraded cables (Norne Zoetic Copper), but still feel I can do with some more impact. I have no issues with treble clarity, however, one never knows what they are missing till they have it. Bass extension will also be a plus - I'm looking more for bass impact here, and if that comes along for the ride, all the better. I'll start with the foam mod and take it from there. This is not to say I am unhappy with the the HE1K. I have always adored its strengths and accepted its weaknesses (based on my perception). I am looking to have it at its peak point and hopefully compare it in the near future to the Utopia.