Kitchen circuits in old house
We are in an old house with less than adequate service to the kitchen.
There are basically three areas for appliances - all on separate walls.
One of these has a triple-gang box with 3 duplex receptacles fed by a new 20amp run from the main panel.
The other two areas have double-gang boxes with 2 duplex receptacles (A total of 4 duplex receptacles on two walls). This is one of the old circuits in the house and there are other receptacles on it in other rooms. It's also 20amp.
The triple-gang box is currently handling the 'fridge (6.5amp rating), the dishwasher (12amp rating) and a micro/convection combo oven (13amp rating) plus an under-cabinet light.
The two double-gang boxes handle various things at various times - toasters, stand mixers, coffee pots, the occasional iron, etc.
What I want to do is this:
Run two more 20amp circuits to the triple-gang box to essentially create a dedicated receptacle for the 'fridge, oven and dishwasher.
Run a new circuit to each of the double-gang boxes.
I have the room in the sub-panel for the breakers, but have other questions:
First, is there any problems in the "theory" of what I want to do?
The existing run to the triple-gang box, as well as the two new runs would need to be in the same panel because they need to be tied together to trip as one, correct?
When I eliminate the current wiring connections in the two double-gang boxes I'll be left with an interrupted circuit - assuming there is the appropriate volume in the boxes, can I tie together the old wiring inside those boxes?
Even if I can do the above, would it just be better to pull the wires to the basement and tie them together in their own work box?
And finally, what are the cons to using double-pole breakers? This will max out the number of spaces in the panels and anything added in the future will require another sub-panel or the use of double-pole breakers. (The main panel is a 30-space, 40 circuit and the sub can also accept the doubles, though I don't remember the rating without walking to the basement.)
Thank you very much! Any and all thoughts are appreciated.