After both Verizon Wireless first and second tier support, and even Palm support told me that the Palm Treo 700w must not support stereo – which, of course, doesn’t sound conclusive – I heard from both internal distribution lists and external forums that the Treo does, in fact, support stereo sound and that some headsets – like the one I was recommended at the Verizon Wireless store – do not switch impedance to indicate to the Smartphone to switch into stereo mode.
After all the misinformation I was given and before I posted I wanted to make sure this was the case, so I asked Palm Support for a definitive answer and got the following back (only relevant text shown):
I can definitively inform you that the Palm Treo 700W has a 4-pin 2.5 mm jack that is capable of outputting stereo. A stereo headset adapter, sold separately, is required for use with standard stereo headphones. You can find both the Treo stereo headphone adapter and the Palm® 2-in-1 Stereo Headset from Palm Store online via the link below.
Of course, other manufacturers make compatible stereo headphones – some with dual function to service as a hands-free headset with the click of a button. The approach recommended to me elsewhere is to get the Palm Treo Stereo Headphone Adapter so that you can use the more common 3.5mm stereo headphones, which is likely what I’ll do.