best machine for low back problem

[fatjack]

I'm almost 60, have had low back problems [sciatic] for quite a while, probably agrivated by being 30lbs over weight and finally i'm doing something about it.....for my birthday i'm getting myself an excercise machine and internet research leads me to getting an elliptical type machine. that way i could work out at home while watching tv. any comments on ellipticals for low back problems??