What are your thoughts about moving up product line(s) within a Company?

I guess I'm gonna be the outlier here!

I bought my Vandersteen 2Cs about 25 years ago at a local stereo shop.  Had many satisfied years listening through them.  Then RV brought out the Model 3s.  Met RV at the Stereoshoppe in Selinsgrove, PA as he launched his newest design.  I was seduced by the considerable jump in dynamics with the 3s and bought them.  After several years, RV came out with the 3A and away my speakers went to Hanford, CA for the upgrade.  Richard significantly tamed the high end in that incarnation of the model 3.  Several more years passed and then the 3A Signature was offered.  Another trip for the 3s to Hanford.  I enjoyed the 3A Sigs. until June of 2016.  After reading much about the new Treos and then the Treo CT I decided to take the leap to the Treo CTs sight unseen and unheard.

Why?  Our neck of the woods, which at one time had three fine dealerships now had none at all.  None.  Because of my 30+ years with Vandersteen speakers, and the experience with the upgrades to the model 3s, seeing where RV priced the Treo CTs at in the totality of his line I had a pretty solid sense of what they would sound like.

Fortunately for me, after making a necessary change in speaker cables to accommodate the sound of the Treos, I am hearing a refinement to music that I really didn't know was possible before.  

As so often happens, once you realize an improvement on that scale you begin to wonder how much better it could get if you ....

In many speaker vendors lines, you can upgrade by going to the next model. For me this has occurred with my ushers, and in the past with totem and others. 
But upgrading to the next up the chain speaker might involve upgrading your equipment. For my totem model 1’s, I used a nice 200 watt classes or McIntosh amp. When I moved up to the Mani 2’s, the best sound came from teaming these up with McIntosh 1000 watt monoblocks.
same goes moving up the chain with ushers and revel. You need in many cases more power with a larger speaker

I purchased a VAC Phi 110 because I liked my VAC PA 100 amp and Renaissance pre so much.  I thought moving up the line would be a big improvement.  It didn't work out that way.  Luckily I still had the PA 100 which I still own today.  Just goes to show you, there are no guarantees.

It depends....
for companies that keep relatively stable and defined key principles then yes a move up the line ( assuming you can drive them and or the room is OK acoustic wise in the case of speakers )

so for example Ayre, Vandersteen, ARC, Aesthetix, Basis....
the designers have a pretty strict set of design principles they believe STRONGLY in and as you move up the line it is generally scale and quality of execution - as was pointed out in the story of upgrading within the Vandersteen Line...

I had two very positive experiences moving within manufacturer’s lines:

I had Thiel 1.2, followed by 2 2, and then 3.6.  All had similar signature and each move brought great improvements across the board....still miss the 3.6’s.

likewise, I had Audio Research LS3, SP16 and then LS26.  All three were more alike than different and each change was a terrific move forward.

So, similar products within product lines have been good for me.  That doesn’t mean I would necessarily enjoy Audio Research’s Class D hybrid amps, for example, because I like their line stages, a completely different product line, of course.

I agree that an in-home audition is the only way to know for sure, but having prior experience with a manufacturer, knowing the house sound and design ideals, is very helpful to me in choosing new equipment.