In a small bathroom, less is always more. If you include a vanity, you will probably need to choose a very small unit. Depending on your needs, you can choose the style (cabinet or drawers or a combination) that is most suited to your needs. Recessed medicine cabinets (set into the wall, with an unframed mirror) are ideal in small bathrooms.
The price of wall mounts can vary widely, and even though the cost may be small in comparison to the cost of your TV, a lot of people find that even the most basic types of mount can actually be relatively expensive for that they are. If you already have a cabinet to house your receivers and other equipment, it can look slightly odd to see the TV mounted to the wall instead of placed on top of the cabinet.