I am sorry but I was in Madrid twice and this Post officce building is for me the most exceptional building there. Btw. https://www.google.com/search?q=madr...jCMMWRaMSyosAP
Prado is by its own very nice museum with fine Goya collection but..... if you have just limited time to travel you really do not wish to spent one day in museum spaces. If they would notice that they are art fans I would suggest that, but from all above written I do not think so.
Madrid is just large city with wide streets and lots of motorbyke (as everywhere in Spain) traffic, but it has honestly rather average architecture and average live atmosphere. Compare it with Granada, Seville or Barcelona ...!

And short message for Sassafrass : Suggestions I gave were real, links I posted where real...., so thanx for blaming me.
But if you wish to come to Prague, you are welcome for real beer

I would cut out Madrid and add one night to Rome and Paris. I would also probably drop one night from your German city and add it to Venice.