The introduction of a new Volvo is such a rare occasion that it deserves to be noticed. Change comes slowly to the Swedish firm, which tends to keep good products in its catalog far longer than industry norms. With the new S70 and V70--plus the soon-to-arrive C70 coupe and a later soft-top sibling--Volvo is revealing both a new car and a new model designation system. Said system, in which S denotes a sedan, V a wagon (and, perhaps, a rumored sport-utility machine) and C a coupe or convertible, is combined with a number that applies to an entire line. S- and V90, for example, are the new names for the current 960 sedan and wagon. It's not entirely correct to call the S- and V70s totally new. There's a strong resemblance to last model year's 850 that will be readily apparent at a glance. Good reason: The 70-series sedans and wagons are mildly facelifted 850s, with some improvements made where they count most and a new face that follows Volvo design tradition but is more up-to-date. But the 70-cars are new enough to warrant a good, long look, and keep enough of the virtues 850 owners prize to make them attractive replacements for those cars when trade-in time rolls around. Even in a competitive class, in which they must contend with the C-Class Mercedes, 3-Series BMW, and Lexus ES 300, to name just a few, the 70-series Volvos have much to recommend them.