Grand Sichuan (multiple locations), Szechuan Gourmet (located in Midtown West), Lan Sheng (ditto), and a few others.
For Hunan, your only real option in NY is Hunan House in Flushing. Fortunately, I think it's one of the top Chinese places in NY and should be worth the trip if you're seriously interested in the cuisine. You can also get your fill of Sichuan in Flushing (Little Pepper, Szechuan Gourmet, Spicy & Tasty, Chengdu Tian Fu stall, etc.). Do a search in the Outer Boroughs board.