I recommend using a pesticidal oil (neem oil or sunoil). The dish-soap works, but I am all about taking no prisoners when it comes to pests in my orchids. Do be cautious with the cinnamon as it will be problematic with the orchid roots.
Most of the DIY / boxstores sell their orchids potted in sphag. This is good for the vendor shipping the orchids because it is lightweight. It is often the death of many Phalaenopsis too because of the amount of water the sphag can hold causing the roots to rot. It is a good habit to repot all of your new orchids to make sure you know 1 - what the root condition is and 2 - that you make sure there are no pest hiding in the medium that could eventually harm the new orchid or your other orchids.
Pot size does matter, but only because of watering. There are lots of people that grow their orchids in sphag and have no problems with it at all. This is because of how they water. If your orchid is potted in too large of a pot, then most likely it will not dry out fast enough to allow the roots to breath. If, however, your mix is something that doesn't hold much water, then it could dry out faster. It is really all about balance. Phal orchids like to stay moist (not wet). Since, like paphs, they do not have p-bulbs, they have only their leaves to store water. This means water intake and gas exchange through the roots is very important to phals.
Here are some articles to help:
How to repot a Phalaenopsis orchid - video demo with instructions
Growing the Phalaenopsis Orchid (Moth Orchid)
Phal-a-normal: So What's A Phalaenopsis Supposed to Look Like?