In the Champions League, no opponent should be underestimated by any team, especially when it has entered the knockout stages such as in the quarter-finals. This means that every opponent must be seen more seriously by any team if the team wants to be in the next round and win with enough aggregate goals to be able to qualify for the other round. Aston Villa is a fairly serious opponent and I think PSG also sees Aston Villa as a dangerous opponent because in the Champions League all abilities will always be deployed by any team without any fear, especially if the team no longer has a chance to become champions in its own domestic league.
PSG is strong team in French League and is close to winning record 13th French title, right now PSG is number one team on points table of french league. Villa is an average team in EPL with 12 wins this season and is at number 9th position on EPL points table. Odds must be in favour of PSG for there upcoming quarter final with Villa but still they must take the quarter final seriously. In football anything can happen, we have seen many instances where mediocre team was able to beat top teams of a League.
Yes PSG is a powerful team in the French League and we have seen that they are already in the closer to the 5th title win. Yet the way the French club is performing will also be confident that they will be able to win the title again. Their opponent will be their opponent in the quarter finals, the PSG team may destroy Estonvilla in their first leg match at their home ground. Yet, as you say, these two teams must take the quarter finals seriously. Moreover, it seems that the PSG value in the Champions League can be much higher, but the estronbila will not be easily reduced.