A 7.5 pot and you will need to watch for boilover closely
8.5 is better, but the 7.5 will work
the advantages of full wort boil are a few, the density of the sugars are the same as an all grain so you do not worry about caramelizing the sugars. however add the extract at about 150 degrees and stir while adding, that way they will go into suspension real fast, at 70 degrees they do not dissolve as fast and carmelization can be an issue
Hobs utilize better at lower densities also, a good recipe or extract will use 15 to 20 percent more hops than the same recipe for an all grain. that is because most extracts are partial boil and all grains usually are full boil and the hops do better in the lower density wort of a full boil
with full boils most guys already will have a wort chiller and they can chill the wort down fast, which is a good thing as it means leaving a lot of stuff in the pot that can be transferred with hot wort. Plus the longer you let that wort sit outside of the fermentor the more chance of catching an infection.
Lots of benefits to full volume wort boils, only negatives are cost of equipment.