Naturally, I am a bit biased as there are certain White's detectors that I feel deserve to b considered 'All Time Favorites' and 'All Time Dollar Values' based on features, performance, versatility and durability.
In their day, some of the BFO's and TR/TR-Disc. models would fit in that group, but reality says we need to consider the most fitting and functional models of the past two decades or so. Sadly, many/most of the greatest models White's has offered have been discontinued, but they remain top sellers in the used detector market, and for good reason .... they work well!
My 'favorite' list during these years include:
MXT Pro and M6, of those in current production. I know a case could be made for the standard MXT, but the MXT Pro bumped it on my listing. I used to keep an MXT & M6 in my personal detector battery with a couple of other favorite models, but used the M6 most often. It wasn't because of the Tone ID because I very seldom use it. It's only an occasional-use tool for certain applications. I just like the fit-and-feel (similar to the Classic ID and IDX Pro due to the housing and rod system), and the simplicity ... all while providing the rapid automated GB of the MXT and the same great Sensitivity control system and full-range (zero-Disc capable) Discrimination.
The MXT Pro, w/5.3 Eclipse mounted, is in my current arsenal because it fills the services of both the MXT & M6, plus provides me the Back-lighted display for hunting during hot summer nights.
Also, the:
XLT
6000 Pro XL / XL Pro (back in my current arsenal w/Royal 800 mounted)
Classic IDX / IDX Pro (the IDX Pro w/Blue Max 600 is in my detector battery w/Mr. Bill's modifications)
Classic ID (also rides along on my 'detector' seat w/4" Snooper coil mounted for super trash)
Classic III SL
Classic III-Plus
I'm not at all surprised that the M6 is finding stuff for you, an as times goes by you'll find it has to be one of he absolute 'best buys' on the market today. Keep hunting, and I also envy you that you have a wife who enjoys this grew sport with you ... or visa-versa.
Monte