Same height for all boxes

My customer wants all boxes on the front page of http://www.haus-der-bilder.de/wp2/ have the same height. I have already kinda managed to get there by adding fixed height values to a) the text part of the box and b) the picture part.

This one gives a fixed height to the text part (headline and if needed description text):
.entry-container {
padding:2.9%;
margin:0;
height: 80px;
}

And this one gives the picture part inside the box a height of 200 px:
figure img {
display:block;
margin:0 auto;
height: 200px;
width: 100%;
}

At the first glance this looks fine.

But when you take a closer look at the pictures the proportions are wrong:
“Girls want to have FUN” – original height was less than 200 px and it got stretched to 200 px
“PoP Art @ Haus der Bilder” – original height was more than 200 px and it got compressed to 200 px

I have tried quite some stuff like this but couldn’t get the proportions back:
.wp-post-image {
display: block;
width: 100%;
overflow: hidden;
}

I even wouldn’t mind if the picture is cropped to its top 200 px – but the proportions need to be correct.

Can anyone please get me an advice on how I can get back the pics’ proportions?

Your help would be appreciated a lot…

Thanks
Scherli