Suggestions for the next piece in my collection

[Connaught]

I have been fortunate to be able to collect a number of great watches over the last few years and my grail watch has always been the 15407ST. Although the steel and gold openworked models have now been discontinued I am hoping when the new iteration is released this year, it will be equally as special and would like to work towards getting that at some point.
I currently have the following pieces in my collection and am debating which direction to go in now, in order to bring my journey closer to getting my grail, I also have other pieces but they were purchased a long time ago and not with my current SA/AP House:

26420SO taupe
26240ST blue
15510ST black
15550ST grey
77451ST blue
15212NB

As such, I am open to suggestions from fellow AP collectors as to which piece would help bring me closer to getting my grail, perhaps a precious metal RO? or perpetual calendar? I think I could get the stainless steel jumbo but I suspect that would push the openworked further down the line for me…
Looking forward to hear your suggestions. Thank you in advance!