I've been running the SP-One with the bigger brother IDA-8. If the IDA-6 is cut from the same cloth, this will be truly a fantastic pairing! Very smooth upper end, almost a bit laid back. Lower end is amazingly strong all the way down (considering its driver size; we're not expecting subwoofer levels obviously) and beats out my other bookshelves of the same size for reach.
One thing I'll note though is that due to rear port the SP-One likes to have a bit more space behind it, otherwise it gets a bit muddy. Putting it up on stands was helpful, but not as important as taking it away from the wall in my opinion.