Laptop Advice

[frcguy]

So, I know I made a thread about something similar to this back in December. However, I've got a more specific use case this time.

I'm looking for a laptop to replace my aging 2010 MacBook Pro. While I would love to spend $2K on a new MacBook Pro, I don't have that kind of money and would rather do that before I go off to college so it isn't obsolete by that time. So, I'm looking for something in the interim. Here's some things I'm looking for:

• Runs Solidworks
• Good battery life
• Upgradable RAM, HDD, etc.
• Fast CPU
• Somewhat durable (not going to be running a truck over it, just want something that will hold up to, well, a high school student's life)
• Preferably discrete graphics
• Preferably 13" screen (but if the screen is bigger that's not a deal breaker)

And the main criteria:

• Under $800

There may be a little fudge factor going upward from $800, but I want to keep it as inexpensive as possible. I'm happy buying used off of Ebay, and I also am comfortable upgrading it after I buy it if that's a solution as well.

You all were quite helpful last time with a question like this, so I am excited to see what everyone thinks!