All the items with which that liner's compatible are listed under Product Information on the link you provided. Not sure what you mean by "additional liner" though. If you have to pick just one, I'd go with the warm pile liner.
Where I live, it's consistently below freezing during the winter months. Most days last winter I wore a crewneck sweater, button down and Bedale (with the warm-pile liner). That was enough to keep me warm.
Just picked up a pair of MacAlister boots on sale for $45 (about $100 less than the original price). I've only had them for a week, but I actually think they're better than Clark's desert boots.
They're on sale online with an additional 50% off if anyone's interested. Might actually buy a second pair.