Upload & Sell: Off
I work as a Business Systems Analyst and have to do this analysis for customers all of the time. Determine the most cost effective course of action, do nothing, upgrade, or replace. It all comes down to what you need and can handle... cost vs performance.
While I love the speed of the SSD in my laptop, the size limitation can be a hassle. In the course of a few busy days I can shoot more that it can hold (128gb - software). Since this is primarily for travel I have not done a clean reinstall to make more space. However, if your laptop is your primary system this could be problematic.
A Desktop is cheaper and faster, but not portable.
An Ultra-light Laptop is fast and portable, but limits storage and are expensive.
A Standard Laptop can be fast, with good storage, but are not as portable.
All of that being said, I don't think the cost of the memory upgrade will give you the bang for your buck. The SSD would give you improvement, but may greatly reduce your storage capacity. Waiting to replace your system costs you only time while processing images.