When I was back in the world of double prams I had a city mini double for my car/shopping pram and a valco "runabout" double for my walking pram. It weighed a bloody ton but it was fantastic for me and the kids - really easy to manoeuvre, good suspension for the girls, great for the weight range you're talking about. It would definitely be an "as well as" pram though - the handful of times I did have to get it in and out of the car it was a nightmare.

I have also used the double mountain buggy (still have my single) and they're fantastic too. I would have liked to get one of these over the valco but at the time money dictated I went with the valco. No regrets though - the valco was a brilliant double pram.

Check out (if you haven't already) the twins/multiples websites. They often have a really good range of double prams at not too bad a price.