Ya think -- I drink quite a bit to wine and belong to a variety of wine clubs, so I know much more about wines than I did 10 years or so ago. I do not profess to be an expert....I just know what works for me. Your understanding is generally correct. Wines should be stored in stable temps. Ideal is 55, but they'll age well at 60-65 degrees. 65 is tops for temps, otherwise the wine is at risk....I'm talking about the temps of storing in basements, cellars, etc. Generally, reds are the wines that you'll lay down for a number of years. I have some in my cellar that are down for 20-25 years to achieve maximum flavor. This all depends on the wine varietal, the quality of the wine, etc. Many reds are perfectly wonderful to drink with in a couple of years. Whites are more immediate, although there are some varieties which can be laid down for a few years -- but not for the length of time of the reds. For example, I recetnly carried back a Semillion from Australia that should not be drunk prior to 2012-2014. Whites taste best very slightly chilled. As they are in the glass, they slowly warm to room temperature, their "nose" opens and expands, along with their flavor, they breathe, and then you have a wonderful wine. Nothing ruins a bottle of wine more than serving it too cold. Often, I'll just grab a white wine from my "cellar" -- actually my basement, where my wine cabinet is stored -- and open it and drink it without chilling. The temperature by my cabinet is closely monitored to keep it within the 55-65 degree range. In my personal opinion, dual zones are not necessary to properly store wines. If I ever decide to replace my bar refrigerator, I'll replace with a single temp wine refrigerator. For my needs, that will be enough.

My only experience is with smaller countertop wine coolers, but one I used did manage to keep about a 10°F difference between the topmost and bottommost shelves. Not divided into neat zones though; the middle shelves are simply between the two temperatures, the lower the colder. I've never found the standard temperature rules for red/pink/white wine to necessarily be the best though, with for example, shiraz tasting better when served cooler than cabernet even though they're both red, so the variable temperatures proved useful. Some wine coolers work like most refrigerators - they use a compressor. Others don't use a compressor, which have the side benefits of being silent and making more efficient use of space. Both varieties can be made to cool different compartments to different temperatures if designed carefully. You may want to crosspost this question on the GW wine forum too.

I can't comment on the models you are considering, but I have two. One is a Summit in my breakfast bar that has a very soft hum when it kicks on. We don't sit near it, so it's never been an issue. The other is a SubZero in DH's bar in the family room that is totally silent.

How about a AMCOR WV-100? Here is a link that might be useful: Amcor WV100