Kind of hard to tell tw, considering that SolidWorks is not your everyday software that everyone has installed. Looks like a really cool design program that could make some kick a$$ machinery. Without knowing how big the designs are, how often they are updated on the hard drive, the size of the program itself, and other I/O requirements, it is only a guess to say that it will make a noticible difference.
The system specs don't give much of a clue. 6 GB of RAM is recommended, but no mention of hard drive space required. I suspect that the application is CPU intensive, so you may want to consider a beefy quad core with a 1366 socket. That might be a better place to put your cash, but you should confirm.
You can call a salesman and see if he can find a Software engineer that might know. Have you tried the user community? SolidWorks Blogs