Then there were 2

Do not underestimate the Rogue Stereo 100.  It is extremely "clean" with a low noise floor, very good detail and articulation.  Although it is a tube amp, it is not overly warm and is definitely not "diffuse".  I had one paired with Sonus Faber Amati tradition speakers and it was extremely good.  I traded it for the Rogue Apollo Dark Monos which are truly spectacular.  (Primary reason for trade was I felt I needed the extra power and wanted to make the next step in terms of articulation, lower still noise floor, etc.) Rogue is a quiet company. Mark Obrien is a genius in design and is nearly always available by phone to answer questions, discuss the components, etc. Fantastic support.

My reaction is exactly the same as @atmasphere . What are the speakers will you be pairing?

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.

@jimbones What loudspeakers are you planning to use and how big is your room?

elliot that was my preference as well, however they are hard to find used. QS has discontinued them. I agree with your points. The Ref75SE is not too heavy at 47 lbs.

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.

Rogue makes good stuff.  I had the M-180 monoblocks for a long time and they were great.  I own a couple of ARC pieces, but haven't heard the amp you're looking at.  If buying blind, I'd lean towards the ARC.  I would expect it to be just a bit more refined and as mentioned, it's going to have better resale value.

I'm not familiar with Rogue but if it were my money, I go with ARC. The Resale value is better and I know it has great sound quality.   ARC has a sound quality reputation that has spanned decades - they aren't going to ship second hand sound.