Is the post size the same for 50, 40 and 22i?

I am going to get the Denon 2802 within a month but trying to decide whether to go with 40 or 22i as my surrounds (front will be 50, centre will be 150 and the sub will be 175). The speaker cables (AudioQuest Type 4+) will be 30 feet long for the surrounds. What will I gain/lose by going with 40/22i?

The HT (family) room is about 28 X 13 X 9. The sofa is along the long wall and a fire-place is located at the middle of the opposite wall so in reality, the area for the HT system is about 14 X 13 X 9.

Thank you in advance for your advice.

50/22/40