I use, teach, and run tech support for SOLIDWORKS every day and I recommend more than the current minimum which is 8 gigs of RAM, a supported graphics cards, and a SSD. If you can get more RAM then do so because RAM is cheap. As for the crashing itself you can usually help this by creating your assemblies for your robots in such a way that benefits your machine. And don't worry, everyone crashes from time to time no matter what CAD system you use so you are not alone.
There are a ton of ways to make your assemblies faster and easier to work with but the key is really how you put them together no matter which CAD software you use. I have a video here that describes how companies actually lose a ton of money because of poor assembly management and a couple of solutions to the problem which exist in the software. Large assemblies will lead to instability and crashes without some checks in place.
Check this video out and see if that helps before buying a new machine:
https://www.youtube.com/watch?v=Og6nYQ7k2Bw
Our full robot assembly rebuilds in under 10 seconds on student machines and that is because we only have 5 subassemblies in the top level. Most teams I see usually have hundreds of parts in one top level assembly. You can build the parts at the top level and drop them into subassemblies later. Just remember that having tons of mates, complex geometries, and tons of parts in the top level is usually what causes the crashing.
The most complicated parts on most robots are often the transmissions. We save those form a .step file from the manufacturer as a single solid or part because you only need what, 3-4 bolt holes? The rest is just a placeholder.
Hope this info helps!