It seems like for a lot of people (based on reading blogs, forums, etc) eating too few calories ends up being a problem, because your body starts doing starvation-mode stuff, not metabolizing calories the way it would if you were getting enough. I stick to around 1500-1700 calories a day but I think I may end up raising that because it seems like on my higher-calorie days I lose more.
The way to up your metabolism is fairly simple -- build muscle. At least according to my old spinning instructor, who had the most perfect butt of all the women I've ever met, a pound of muscle burns something like 45 calories an hour just by existing, where a pound of fat burns nothing. So, the more lean body mass you have, the more you can eat, even without necessarily pounding out tons of cardio.
Lifting weights can be intimidating (even after doing it off & on for years I feel kind of sheepish in the weight room with the boys), but it really helps and you can eat way more!
Just my $.02, good luck figuring out what particular combination works for you!

