IMO, rowing is the only machine workout out there that's worth spending time with. You've had plenty of suggestions as far as that goes, but thought I'd add to your legs remark. You can make huge gains with your legs just doing body weight exercises in your living room. Once your done with the rowing, if you don't feel like you've worked your legs enough, do a few hundred squats to finish things off. Takes a few minutes and will do wonders for your leg stamina. Squats, lunges, jumping...in my mind, for stamina, those types of exercises are far superior to the low reps of squats with loaded barbells you see people doing in the gym.
Anyway, like I said, for me there's no better machine for overall cardio stamina than a rower. I've never been so inclined, but a friend of mine trained up to doing a marathon on one (C2 has groups that do it together on-line). Amazing results! And if for some reason it's not hitting your legs, there's an easy fix if you need it.