Regarding LP-HP filter as I understad miniDSP Flex is the least expensive solution here. (and it's 800 EUR in Poland).
Regarding other staff. Partially for me R3 vs R7 decision is matter of preference (bookshelves vs floorstanding). I prefer floorstanding.
My idea of completing this is as follows.
1) Buy sources. Wiim Pro Plus is already tested. UMIK-1 will arrive tomorrow.
2) As a side project I will measure current equipment.
3) In the meantime Apollon Audio is building NCx500ST for me. I'm 100% sure on this part of equipment and it has been ordered.
4) When Amp arrives I will do some sightseeing of nearly audio dealers to do preliminary testing.
KEF R7 is available in my town and heavily discounted (may be related to introduction of Meta series)
5) Then I can order speakers via the internet. In EU you have 14 days to return everything without any reasons.
But I want to narrow choice as much as possible.
6) Then I may think about sub. (based on REW measurements and tests)
In this plan the biggest unknown are speakers.
I was thinking also about Revel F206 but they are 2x more expensive in Poland than R7.
What else I should test ?