The S&P 500 (INDEXSP:.INX) has just crossed 2000 for the first time in its history, and while the milestone may be arbitrary it has given investors a reason to reconsider whether they think stocks are reasonably priced in light of the country’s weak economic recovery alongside a five-year bull market. But Fidelity growth manager Sonu Kalra argues that prices could keep going up for years and that it’s still a good time to buy stocks. S&P 500 valuation remains pretty close to historical norms “Valuation remains pretty close to historical norms, above the historical average but not dramatically above it,” says…