Three across car seat decision making

Hello everyone! It's been a long time since I've been here!
 
We have twin boys who are four now and a baby on the way in May! 
We have a 2005 Malibu and are trying to figure out how to do a three across car seat arrangement. After much research, it appears we'll need to get two dino radions for our boys who are still rather small and need to be in a five point harness. Though this is an expensive car seat purchase, it certainly beats a car payment. 
 
But we're trying to decide what to do about the baby on the way. Perhaps another radion since it will go up to 65 lbs? Or maybe an infant seat that is smaller, like a Britax? Or maybe if we get two radions we can even keep our current infant seat? 
 
It's all so confusing.  Any suggestions or ideas? Thanks! 
 
 
 

 

This is a great site for car seat configurations, and here is a thread about the 2005 Malibu: http://www.car-seat.org/showthread.php?t=229680
 
And yes, car seats are definitely cheaper than a new vehicle! We have radians, and they've been great seats. More $ but very, very sturdy.