Thanks for clarifying this.This is correct, the AEB-I has 8 channels built in betraying its' origins as a Majik product where it well suits the 3.5 way Majik 140. Since the 242 is a 4.5 way and the Akubarik is a 5 way speaker you need 2 more channels of amplification and crossover to work with them. The reason why the standard AEB is available in a ten channel version.
Also one minor correction on the fine post by grommeteer. You can drive any active speaker with XLR inputs from a preamp with only RCA outputs. You just need a cable made up with RCAs on the preamp end and XLRs on the speaker end that has been wired properly. I have made these for a number of people using various active speakers from Linn, ATC and JBL among others. Interestingly, when I had active ATC100ASL speakers and the Klimax Kontrol preamp, which has both RCA and XLR outputs, I found it was more musical with the RCA to XLR cable than it was with the XLR to XLR cable. A customer of mine using K350s found the same thing in his system. These cables were made by me using identical lengths (5 meters) of Linn Silver Balanced interconnect cable, Linn Silver RCAs and XLRs and soldered with Lejonklou solder at precisely 677°F. All were also burned in around 150 or so hours before comparisons. So I think you can rule out differences in construction. But regardless of the musical differences, which some may argue, there is no question that RCA to XLR works for this connection, and I feel works quite well. Finally, when making this kind of cable you do not need balanced interconnect cable - I just used it to allow building the cable with either connector on the preamp end. Most of the cables I have made use unbalanced Linn cable and just bridge the negative to the ground pins in the XLR connector. I actually liked the cables I made for my ATCs a little better with the unbalanced Linn Silver wire compared to the balanced version.
I am curious if it would be possible to Exakt link 2 AEBi together to resolve the 242 / Akubarik amp requirement issue?