Skinzy, I tend to think subs without a highpass are not worth the time as it never sounds quite right. Wilson audio makes a pretty good sub controller for around $5k that would allow for the integration. Might not be worth it to you though if you are moving away from the subs.
jab_kib_sz
i am curious if you have tried a higher crossover point. I found 60hz to be where most of these subs come into their sweet spot. Where they slam without sounding like “subs”. I currently use 2 JL E112 and have pretty munched highpassed them all at 60hz. My speakers (JBL 4367) also go down to the mid 30s and a 40-45hz crossover is fine but nothing special. At 60hz the system has noticeably more dynamic low bass. Once I get to 80hz crossover I feel like my system loses some bass texture.
with your speakers so close to the wall they probably do kick pretty hard down low. When I had my Revel 228be (similar size to the Sopra) I had them 5’ off the wall the a high crossover of 60hz was needed to get a flat response in room.