S/H Pot size recommendation

[Um...]

Hi all! This is my first post, but I have lurked for a while now and have gotten a lot of great information for my budding addicti... err, hobby.

I recently picked up a very healthy, albeit completely overgrown Catt 'Magnificent Watermelon Gold' and want to transplant it into S/H, but am not sure what pot size I should transfer it to. It is currently in a 6" pot, but it has many aerial roots as well as a lot of new root growth. Should I keep it in the same pot size that it's in and repot the aerial roots into the S/H medium, or go with a larger pot, or ???

Another question I have is should this plant, which is healthy and thriving, be placed on a heat mat when I make the transfer or can it be left as is? I recently "saved" my Max. Tenuifolia by transferring to S/H, but this plant had little to no roots and bottom heat was (in my opinion) a big contributor to the success of new growth.

Thanks in advance!