If I ever had to sell off all but one... then I'd be getting out of this hobby for good.... I'd want that one boombox to represent the style I like (VU's, twin antennas, good sound, one piece) and offers the greatest ease of portability while not comprimising on mid-volume sound quality...
It would come down to one of these four for me:
1) M90 - the overall boombox king! but negs are finnicky tape deck resistors and logic board as it continues to age and battery hog... truth be told, I'd sell mine and call it cashing out.
2) Sharp GF-9292 - My sentimental favorite, great looks and good sound. Plenty loud, too, but not like M70. The lack of aux-in is a major minus nowadays, and I'd not going to do any mods just to keep mine... Will leave it original. I've got some great pics of GF-9292s thanks to Lyle's setup at the last meet, so I've got good keepsakes. I'd sell it.
3) JVC M70 - This is the undisputed king of the mid-size boombox segment. It trounces many larger boxes and has best push button tape deck ever put in a one-piece boombox. Period. It is also very good on batteries, too. I think on batteries, you can push M70 louder than M90 after about 5 minutes. M70's are going for pretty good ca$h nowadays too... So, with a room full of Nakamichi component tape decks at my disposal for higher end recording and listening, I would probably take the cash for my M70, too.
4) And finally.... that leaves me with the Aiwa TPR-950! Yup... This is the one I'd be most likely to keep for the duration. For sheer looks and good sound at low and medium volume levels, this box can't be beat. And what it can do with only 6 D-cell batteries is, IMHO, truly astounding. It is definitely the most portable of the bunch and has a cool aux-in feature with an auto-detect that can tell you have an RCA cable plugged in an switches off the radio and plays the line level input. The tape deck playback sounds fantastic, too. Also a reliable tape deck mechanism and decent head. However, mine does not record nearly as good as the JVC M70 does and if part of this trimming down meant I also had to give up my Nakamichi tape decks, then I'd probably sell the Aiwa and instead keep the M70 for the sheer quality of that tape deck. Plus, the M70 goes louder and has those extra SW bands in the tuner, too....
If this decision were forced upon me for real, I could realastically come down to a "best-of-99" coin flip marathon between the M70 and the TPR-950, but for now I'll go ahead and say my keeper is this here Aiwa, which I think is the best looking box of the four I mentioned, too... I love the centered analog VU's and multi-colored button labeling! To me it looks more "hifi" than the JVC, too... If that makes any sense...?
I like it almost better than my 777! 
