Broken Rear Coil Springs 2x [UPDATE]

Hello all. Some of you may have viewed my earlier thread here:

Tried to remove brake drum w/ e-brake engage | PriusChat

in which I looked for solutions as to why my Prius was driving so rough. It turns out I have 2 broken rear coil springs. This caused uneven wear and flat spots. I thought I had damaged something when rotating tires, but it turns out it just exposed the problem by putting em up front. It doesn't seem too common, but others have reported it. Would you say that I should just replace all 4 struts entirely? It's a 2007 with 113k mi. It's a Minnesota car so obviously there's going to be some undercarriage rust but otherwise the car is in great shape. Engines seems fine. This guy here recommends putting in TRDs Broken Rear coil spring | PriusChat

Is that even possible? I don't want anything super extreme obviously, but I am always a firm believer in the importance of suspension in any vehicle I drive. I wouldn't mind a decent set.

Also I will need a set of 4 new tires. Currently have the old Michelin Defenders. What's everyone recommending these days? It seems the Energy Savers aren't even available anymore? The new defender h + T - anyone know anything? Good tires? Maybe go with something like Hankook optiomo if michelin is too overpriced.