The market for ancient Chinese works of art--terra-cotta horses, ceramic vessels, bronzes, jades, and Buddha statues that predate the Tang dynasty (a.d. 618 to 907)--is largely undervalued, and there's still a plentiful supply, from rarities with significant provenance to pieces that simply make good conversation starters. But there's a new dynamic afoot that promises to drive up prices: Mainland Chinese are entering the market in ever greater numbers.