I like to have my table low enough so that I am not reaching up when I'm quilting---- elbows bent at about 90 degree angle so that I don't raise my shoulders up. You may need to raise your chair a bit to make that work. If raising your chair to the right height causes posture problems-- then you might want to look into a saddle stool-- that's what I use and I find it much more comfortable than a regular chair.
Rob