"I'm blown away by the speed & agility of my wifes '02 V70. I'd love to find an older model that's as much fun to drive. Am I dreaming?"

No, get a '95-'97 turbo 850 as it's mechanically (almost) the same car. I assume your wifes car is turbo?
In the 850s, the earlier years term for "GLT" didn't mean turbo, it was basically an option package. The fastest 850s were "R's" or TR-5 ('95 term) as those had the most HP from Volvo w/o modifying. The R's will be harder to find and most are auto trans cars too if that's an issue?
All 850s are FWD so no options there. The last RWD Volvo was the '98 S/V 90, 6 cyls and none were turbo.
The turbo engines are just as reliable as the non-turbos IMO but adding turbo does make the engine compartment just a little more complicated, not really a problem or issue IMO. It is essential to know what kind of maintenance the car had before you purchase it as there are a few neglected, abused turbo 850s out there and you wouldn't want one of those.
As for your 760 (turbo I assume?), 150K miles would be "low miles" for me as I now own 2 mid-eighties 740s with far more mileage and have no intention of replacing either anytime soon.