If you already have a compressor (I use a big shop compressor as well...like having it across the garage when it cycles!), I'd save the money there. A few options...
- If you don't have one, get an awesome spray booth
- New airbrush. Get a dedicated one for fine detail, or for acrylics, or whatever.
- Mixing jars (I can never have enough of these)
- Ultrasonic cleaner
- Storage for paints/pigments/supplies
- Better bench chair
- Fresh set of sanding sticks
- PE bending tool
- If you don't have it, better bench lighting.