With the full-size Sport Utility Vehicle beginning to fall from public favor,many manufacturers are pinning their hopes on a new class of SUV,commonly referred to as the crossover. The crossover combines the ride and handling of a car with the high seating position and spacious cargo hold of a large SUV,but without the larger vehicle's penalties for fuel economy and maneuverability. The latest crossover to enter the market is Mazda's CX-7,a sleek,five-passenger SUV with the heart of a sports car. Designed to evoke the same sporty image as Mazda's flagship performance coupe,the RX-8,the CX-7 may be the sportiest crossover you can buy for under $25,000. Although the CX-7's turbocharged four-cylinder engine may be a radical departure for those accustomed to a big V8,we think consumers will quickly warm up to its powerful performance and reasonable fuel consumption.