Then there were 2

I checked, I also saw no used quicksilvers, that tells you something!

My job designing corporate office space, projects typically 18 months start to finish: I told my employees part of their job was to keep me from compromising under pressure. It's always a war against the forces of compromise.

Not that ARC is a compromise as much as: In 3 years, what do you want to wake up and see/hear in your system?

I meant buy anything interesting used or new that you are confident you can re-sell when the Quicksilvers FINALLY arrive. 

For the difference in price too many options exist,

pounds is usually transformers, heavy oversized parts. two quicksilvers at 82 lbs or 1 ARC at 47 lbs?

Personally I like the look of the quicksilvers more, and, think thru the use and related costs of existing or new cables: the different lengths involved if monos or stereo.

it's a fun problem to have, best of luck deciding.

of the two, I would choose ARC

however, I much prefer the Quicksilver Mono 120's, and think this:

Pair of Quicksilver's, with KT150's is under $5,000. 

ARC is $10,000.

I would wait forever for the Quicksilvers, and use something else in the meantime. However long you wait, it is but a speck of time.

Two mono amps can be moved by one person, more placement flexibility, different cable lengths, ....

You could buy a used pair of mono blocks now, use them, sell them when the Quicksilver finally materializes.