Regarding Aston Villa in the Champions League, yes they have really tried because even I didn't think they can get up to this stage of the competition, but the truth is, this particular stage might choke them but hey this is also football where anything can happen at any point in time. Liverpool didn't leave the competition at their own accord, they were eliminated and I see no advantage on them leaving at this stage, because it now this period that they were supposed to concentrate on the competition since they are 13 points ahead of Arsenal in the league with less than 10 games to go.
Aston Villa really try in the Champions League, they attained the stage none think of for them, but this level of quarterfinal is a level that they need to be very careful especially as they are facing PSG that has be very hungry for the Champions League title for long.
Uni Emrey is a good coach, he is an experienced coach that have good coaching pattern, he will do his best not to disappoint their fans because they also have the quality players to withstand PSG physicality even though on paper, they are not up to their standards. For any team that has made it to this stage in the Champions League, they should not be underrated, so we can see a lot of surprises in the Champions League quarterfinal because Arsenal can also shock the world by eliminating Real Madrid.