Before spending big money on a machine, try some cardio DVDs first. You just need a mat and some space, TV, and DVD player. There's a lot on the market you can try, I recommend Insanity if you want your butt kicked in a workout. Your wife may like the Turbofire series if Insanity is too hardcore for her.
I find the intensity, variety of different movements you perform with your body, and the mental aspect of getting feedback from the trainer on the video and watching the other people in the video working hard to do the same workout you are doing superior to experience you get on a machine where you just peform a single motion endlessly. For me, it's just more enjoyable and the time passes faster with the videos than doing a machine workout.
There are exceptions of course, if I want to watch a football game while burning some calories, I'll hop on my Precor elliptical.
Mentally, it's also good to be out in nature so if there's some good running trails or bike lanes you can run/ride close by, try those as well. If it's a nice day outside, I'd probably opt for a bike ride over all the choices I mentioned. That's just me, find what you like and just be sure to get some activity in whatever it is.