A Provari P3 (newest model).
I own two Provari 2.5 (1 standard, 1 mini) and love them. Actually, my daughter is using the mini.
Why Provari? They work so well that I have no interest in
purchasing the P3, but if I had to spend $450 on vaping equipment, that would be my choice for a new mod.
I'd probably spend the rest on the latest rebuildable tank atomizer. I currently use a Svoemesto Kayfun Lite Plus on my Provari, so I
might get the new Kafun 4.
The leftover money would be spent on new batteries, new charger, and e-liquid.
UPDATE: After re-considering the above and my current situation, I'm more than happy with my current gear. I'd probably get new batteries and a lot of e-liquid.