I know Silvercar are Audi's but I'm not sure if they are the AWD version. If there is even mild weather in the mountains, you will be expected, by law, to have 4/AWD drive OR snow tires and chains may be required -- this is all weather dependent and will be governed by CDOT (Colorado Department of Transportation). Failure to do so if you have any type of road incident can be fines of + $700.

For as cold as it already is and the snow that seems to be stacking up in the mountains, I'd count on the drive being in inclement weather and full of holiday traffic. If the weather is bad, it could easily take +5 hrs to get to Aspen. On decent days, with traffic count on 4-5hrs.

Sunday's coming back from the mountains are generally bad, I would expect 1/1 to be especially bad. You *may* get lucky with that Monday being NY day observed and being a long weekend, but I wouldn't count on it. If you need to catch a Sunday evening flight, it may be best to leave late Saturday.