$7000 preamp vs $700 receiver - Is the difference THAT significant?

I'd approach the question this way:

Why not something in between? 

If you're curious about the increase of quality from $700 to $7000, you'd probably be well served by wondering about the increase of quality from $4000 to $7000.

I think I get that you're really just alliterating with the 7's, but it's really worth wondering what happens with the slope of the quality curve up above, say, $3k to $4k.

Instead of looking at used McIntosh gear here, check out Audio Classics.   Any used McIntosh component they sell has been gone over and checked out to be sure it works properly and makes the specs.  You will also get a McIntosh shipping container.  Do NOT purchase a used McIntosh without the factory packaging.  If it doesn’t have the factory packaging, pass it by.   No mater how much bubble wrap is used, there is a 99.9% chance the unit will arrive damaged.  Factory packaging is the key.  

I went from a Rogue Cronus Magnum tube integrated to a Parasound Halo integrated to a McIntosh integrated in system 2.  The McIntosh sounds so much better in every regard.  I purchased used from AC, have owned for a little over 3 years and it has never failed me.  I listen to it every day.  System 1 has a McIntosh C2500 preamp and MC302 amp.  I love this system and am listening to it now.  I am hooked on McIntosh.  

I doubt you would notice any difference. Since you have always wanted a McIntosh I’m sure it would be lightyears better in a sighted listening test but in a blind one I doubt you could tell one from the other. So get the McIntosh and fulfill your blue meter dream or get the pre processor that integrates with your HT and quit worrying about it. Or get a McIntosh pre processor. 

@djones51 Yes... this is the "thing" that I'm afraid of.  While I have no doubt that I'll enjoy it (and the future updates to my stack), it's that little voice that is going: "Are you REALLY gonna notice a $5K difference in sound?"

@hilde45 I've always been a proponent of "buy it once", "don't go in half-way".  And I kinda made that compromise with the outboard Amp I added last year... knowing that if I got to a point, it was going to be pushed to the corner, in favor of a "pretty blue" meter'd piece of metal.

@markusthenaimnut Exactly my mentality.  I just wanted to hear some folks go: "Yeah, there is SOME audible difference..."  And thusly, I'm truly in no hurry.  The first bump in that Amp500 was eye-opening, and the speaker upgrade (with some new cables) really gave me a hunger.  I'm gonna be cooped up here in the winter with very little else to do... may as well make these upgrades.  :)