carpet/pad recommendations?

May I ask for anyone's experience in putting in new carpet?

We're (finally!) replacing that in our willow glen eichler. I understand we need to get a pad with minimal R rating to maintain efficient use of our (still working) radiant heat.

Are there specific types or brands of pad that are recommended? For that matter, any carpet shopping experience you can share is appreciated.

Is there a carpet retailer/installer that is known to specialize in eichlers?

thanks,
~ malcolm