I have Performance Women's Triflex Tights: (on sale for $55)
"Our warmest tights! Six strategically placed panels of windproof, waterproof Triflex and breathable, heavyweight brushed Dryline. The entire front, crotch and rear center panels are completely windproof, and lighter rear and waist panels help dissipate heat. Articulated, anatomic knee panel, banded waist with drawcord, leg zippers with reflective piping, gripper elastic openings. Black (BLK). Sizes: S(24-26), M(27-29), L(30-32), XL(32-34). USA. Compare at $100."
They are _very_ warm, but _very_ breathable. I love them. They are _pretty_ water-resistant, but for hours in a downpour, I am still looking for something totally waterproof. Right now I have REI Novarra Stratus Womens Rain Pants (cycling-specific) but it of course hasn't rained since I got them, except for the one time I decided not to wear pack them for a Century. They seem very nice, but would not be very warm without tights underneath. I'm going to write a review if it ever rains again.
If I were you, I'd try the Triflex tights, and see if they are enough. They are _very_ versatile for just cold in general, and very comfortable. I wear them over any bike shorts, because they have no chamois. I have never been cold in them, but I have only worn them in the upper 30's, up to the mid-60's. (Where they are very warm, but not unbearable if you don't have anywhere to put them if you take them off.)
PS, let me know if you find the _perfect_ pants!
Nanci