Note: I m assuming that by "RCA" You are referring to Composite Video.
1.) Going from HDMI to RCA is a non starter. Since you are going from a digital source to an analogue wource that's going to require at least a couple of DAC's which are active components so it's gonna get expensive fast.
2.) Going from Component to RCA is possible but it's still not easy. Component video is where each colour is represented by a baseband signal varying between 0V and +V. Composite video however is where the signal is transmitted in a completely different way.
To keep backward compatability with old television sets it transmits a black and white signal on the baseband - Y = R + B + G (Luminance). Then it sends the colour information as a Quadrature Amplitude Modulated signal 5MHz above the baseband (Chrominance). X = B - Y and Z = R - Y. From these one can reconstruct an RGB image.
This is non ideal because there is no direct information given about the green signal, but this is not too much of a problem because the eye is very sensitive to green so it compensates. It is also non ideal because all of this information has to be demodulated at the other end by passive bandpass filters. This results in a loss of image quality across the board.
S-Video is better because the colour information is carried on a separate pair than the luminance, hence requiring no demodulation. However it is still not the best.
Component video offers the best analogue picture quality, which is why apple chose it.
HTH
Chris
