I have a pair of KEF 104.2s, four 102.2s, and four 102s. I don't use my KUBEs with any of them. Instead, I use two Velodyne HGS-15s with the 104.2s and 102s (2.1 & 5.1) and an HGS-10 with the stacked 102.2s (2.1). Cross over to the sub at 80 Hz and don't worry about the roll-off frequency. Crossing over at a higher frequency relieves your amp and speakers of LF duty, leaving it to the sub. I think you'll find that your mains sound better without LF duty, more open with a greater sense of air and transparency.
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