I made a similar decision a year ago, and replaced a 36" gas cooktop, with a Bluestar range. One of the best decisions I ever made! ... although I must admit the old Thermador cooktop served us well for over 25 years;)

We have an oven/microwave combo (KitchenAid). If I could redo my kitchen I might do that part differently. I did not know when I designed my kitchen last year that microwave drawers were a thing. If I had known I might have chosen that with a built in oven instead. I do not dislike our oven/microwave however I do have concerns about the microwave breaking. The fan was actually broken when we installed it, and we had to get it repaired. So if something happens to it, I know we will have to pull the entire unit out to get it fixed which is more of a pain than just fixing a microwave. The other issue I have with it is that microwave is a little higher than I would like. We installed the unit 1.5" higher than they recommend (so I could have a 15" drawer below) and since I'm only 5'3" the microwave is a little bit high for me. Even installing it at suggested height would still leave it higher than the ideal. A drawer would be a nicer height most likely. I definitely like having a separate gas rangetop and built in oven. There are many reasons I want them separate, so a range was never an option for me. But I probably won't combine the oven and microwave again if I did another kitchen.

My daughter replaced her double oven wall unit with a single wall oven and a microwave/speed oven. Since her cabinet could only accommodate a 24” wide oven ( She was not replacing her cabinets and consequently her countertops), her replacement appliance options were very limited. If your cabinet is for a 30” wide oven you won’t have that problem. My daughter needed to add a shelf to the cabinet for the microwave to sit on. She needed to add some wood trim between the 2 new appliances to cover that shelf and a gap because the cabinet cutout height was slightly taller than what see now needed. She also needed a 120V outlet added inside the cabinet for the microwave. As Michelle stated in her post you need to look very carefully at the specs for the new appliances to find those that best fit your cabinet height and width. AJMadison’s website is good for researching appliances because it allows you to filter by height and width among other parameters. Here is a before picture The after picture below is from the opposite angle but you can still see the wood that was added between the 2 appliances. You can also see that changing to 2 separate appliances allowed her to get rid of the over the cooktop microwave and get a vent hood.

Bosch ovens are quite reliable. I recently remodeled and installed the Bosch Benchmark side opening oven with a Sharp microwave drawer under the oven. I had to upgrade my electrical panel as current Code required that each major appliance be on its own heavy duty circuit and I went from a stove to wall oven, microwave drawer, hood, dishwasher and refrigerator. My remodel required a new electrical panel which was costly but not as expensive as it might have been. As The Cook's Kitchen posted, the actual cost would depend on the distance from the main source as well as difficulty in running new wiring. I live in a high rise and was lucky because I was relatively close to the "source". My next door neighbor was not that lucky since he was too far from the main source and so his new panel required a much more costly installation. My advice is that before you make such a limited choice, you get an electrician to determine what would need to be done and what it would cost. While no one is glad to spend money - especially on inside the walls kinds of things :-) - my kitchen electricity was really substandard and not up to Code as it had been installed in 1965. My old outlets weren't GFCI and I couldn't run the counter microwave at the same time as the toaster :-). I also gain peace of mind as God knows what the electrical connections for the old Caloric electric stove were :-).