This is just my opinion of course but I would see this as more a limitation of the iMac than anything else. That's why I got a Mac Pro - not because I really need all the number crunching power as the stuff I record is mostly acoustic duo with a VERY small track count. IOW an iMac or a MacBook would do the job perfectly well in terms of running the DAW (Logic) and plugins. Where they fall down severely is in terms of peripheral connectivity, especially FW. That you have yours working as it is with so many things daisy chained is something of a small miracle - especially with an audio interface (any!) and a Liquid Mix
on the same internal bus to say nothing of external drives.
Anyways maybe you CAN repeat the miracle - this maybe more about how you specifically happen to use the gear. For example if you had a back up drive that was infrequently used daisy chained to the R16, or you don't use the external drives to stream samples at the same time that you're trying to use the Liquid Mix
. . . the only way to be sure is to get one on a trial basis on a credit card and send it back if it doesn't work.
Me, I'm waiting for the R24 - not because I need the extra tracks, but because I think we're going to see A&H having learned many valuable lessons with the R16. That means a LOT of guys doing pro/semi pro work will want to sell their R16's - maybe to a hobbyist like me!
That said, lovekrafty has me seriously intrigued about what goodies might be coming with the R24 - and little hints about connectivity are just fanning the flames!