As a longtime 740/940 owner, I made the move to the FWD's with trepidation (I'm not a fan of FWD in general). But so far, I've been very impressed. To answer your major questions:

Build quality? The 800 / 70 class is higher quality than pre-96 900's. Quieter, smoother, nicely appointed. The tradeoff is they're a little smaller, and the turning circle is pathetic. End-of-life '96-98 960's (in '98, S/V90) are better quality than previous years and may be of interest if you want the RWD along with some of the nice stuff in the 850. Late model RWD's have most of the same stuff (cd players, climate control, winter package, seats, instrument panel design) with an early implementation of the same inline 6 engine that's in the new S80.

Reliability? These cars are more complex than the 700/900 class we're used to. But the engineering is well thought out and there are no superfluously over-engineered aspects to the car. It's a good balance. Not as bulletproof as the B230/B230FT engines, but the problems aren't with the nifty 5cyl engine (a Porsche design) - the problems have been component level. By now, most will have been fixed under warranty. meticulous, on-time maintenance is the key.

You'll like the FWD, but I highly recommend a turbo model.

Good luck.
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(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)