I hate low ovens. I love all ovens at optimal height (something my mother has in her tiny kitchen). But with the gas oven, I'd do it in a range given the limited wall space. A range is classic, and since you're thinking Blue Star you obviously want a top notch gas stove as well. And just on looks, I think three different ovens from three different lines all clumped together would look motley, and I'm into buy each appliance for its functional value. The Advantium and Combisteam clash enough to start with. If you put the gas oven in the range, it not only takes it out of that design adventure, it gives the blingy range as a great focal point to take the eye off the mismatched stack.

I have the combisteam over the Gaggenau single convection. I might have been able to squeeze them side by side, using the 24" combi (same oven size--the extra six inches is for looks), but with the way the controls are positioned it would have looked really weird, so I stacked them. I stacked the Advantium with a warming drawer on the other side of the kitchen.

Have you checked the specs and recommendations to make sure you can stack the Advantium and Combi?

Are you sure you want a gas oven, rather than the Gagg? The moist oven you get from burning fuel can be gotten in the Combi, and if you need it in the larger oven you can just put a ramekin of water in. The best Advantiums aren't supposed to be mounted below counter, but if you have a place you can sneak it in separately at height, the Gagg pair would also be a good choice.