I've been wearing Pearl Izumi Select Thermal Tights (with shorts underneath) that I got a couple of pairs from Nashbar for cheap (they're a 2012 model I think). They're 25% off today, so can be had for $33 bucks a pair plus shipping. They're pretty warm, but below 40F might not cut it (I haven't been out yet when it's been below about 45F). They have XL and XXLs. I'm 6"2'/260lb and wear the XLs, but my legs are pretty lean/muscular now after 2500 miles of cycling this year (gut/moobs are a different matter sadly).

On top I usually just layer, with arm socks and a I have a PI thermal barrier jacket below 50F.