Heidegger came in the wake of Hegel and Nietzsche as a type of existentialist who wanted to do without a metaphysics, whose experience of the world was always and ever an experience of space-time existence and nothing but. He’s one of those characters who are willing to shift the old meanings. Transcendence, if anything is an arch-epoch of human existence in time.
Kant, who said he finished what Plato began, is really an Aristotle who works inside after declaring the outside inaccessible. But his reasons are different for finding things inaccessible. It isn’t a practical consideration as it was for Aristotle. It is more logical and conceptual. Like Aristotle, Kant accepts the givenness of the world, but it is through conceptualization whereby the contradictions or paradoxes are resolved. Such is the hallmark of a scientistic “metaphysics.” The nous has become the fully revealing god of a phenomenal kingdom. Who cares about noumena after that?
In short, three different socks that don’t match.
Now that was funny ... and worthy of my College Philosophy teacher who thought the discipline to be the only subject deserving of college status outside of science and math classes. He was always hungover.
I approach the quandary from a different perspective, i.e. what a beginning means.
In the absence of time, events cannot occur.
The origin of space/time is a more fundamental issue in every discipline than is the origin of energy, the origin of information and the origin of life v. non-life/death in nature.
In making a beginning of all that there is both spiritual and physical, God created space, time, causality, events and things - i.e. existence.
Which is to say, existence has no meaning apart from space/time, which is geometry. Even spiritual beings and eternity itself cannot "be" apart from time.
Moreover there is nothing of which any of these can be made but God Himself or more specifically, Gods will whether His creative will or His permissive will or some other type of will of which I am unaware.
No God, no existence; no Beyond, no here. To that extent, they are complementary but the reverse does not hold. God is (I AM) when every other existence is not, i.e. in the absence of time, God is. He is the only possible uncaused cause of "all that there is."
Those philosophers and scientists who formed their theories and systems before the measurement of cosmic microwave background radiation in the 1960s could appeal to a steady state universe and thus rationally justify a reduced sense of reality that all that there is is that which can be perceived by physical senses or mental reasoning, i.e. rationalize their atheism and politics or ideologies based on it.
Since then, the ever consistent, accumulating evidence is that space/time is created as the universe expands. And it is not just expanding, but accelerating. IOW, there was a beginning of real space and real time and therefore, physical causality, energy/matter, things and events. At the very minimum, there had to be an uncaused cause of the geometry, i.e. God.
Nowadays, all the atheists can do to justify their hope that God does not exist, is to theoretically push the beginning backwards to prior universes, prior causations. This is the plentitude argument, that anything that can happen, did. However, the plentitude argument requires an infinite past (space/time) and thus, these theories are merely obfuscations because whether brane theory or something else, all cosmologies rely on geometry for physical causation!
In sum, without an infinite past, no one can rationalize denying God the Creator. And there can be no existence - spiritual or physical - apart from God's will.
Plotinus was quite the jokester and sometimes it is easy to forget that he was pre-Christian. He apologized every day for presenting himself in corporal form.