Re: Pochade boxes and tripods
If you're going to go Sienna style, take a look at the copied version, Soho, at Jerry's artarama.
There are many styles of pochade. Really depends upon how you paint. If what you want is really an easel and palette platform, there are less weighty ways to go. If what you want is a box that also carries supplies and is an easel, that's a different choice.
In all, a photo tripod version (which is what I use) has to cover these bases: 1) be sturdy at the height at which you paint; 2) have a strong enough head mechanism to withstand the weight of your box/easel and the pressure you will put on it as you paint the canvas. For many photo tripods you can replace the head and it's not terribly expensive to get a heavier duty one. For example, I had to replace the head on my Dolica with one that cost $30 and handles 20 kilos - truly sturdy.
Someone posted a great URL for a review of types and models/makes here on Plein Air forum.