No, -43.7dB isn't particularly good. Personally, I'll consider -60dB or so to be decent. However, RMAA measurement is strongly influenced by the measurement tools and load, and therefore there really isn't that meaningful when you look at those number. Plus, the output impedance and power, which are also quite important, ain't measured. Simply put, RMAA is more for picking out obvious problem rather than showing how good a source is. It has its limitation.