I currently have a couple of Dell Precision M90s that I use for basic Solidworks modeling.  No huge assemblies or large/complicated files.  The computers are heavy and showing their age but do OK overall.  The one nice thing about this model is that there were a lot made so there are all kinds of parts and accessories.  I hate having to bake the video cards every year though to fix the graphics cards (reflow the solder).

I'm looking for the next step up and will relegate these two workhorses to other tasks.  What's commonly available used in a 17"+ laptop for running SW 2013 with Win 7?  Preferably something under \$800 that I can pick up on a big auction site.

Thanks.