A phenom II is enough power for most users as well as being less expensive allowing for things like a better GPU and more Hard drive space. If you need more performance then you need to be looking at the i7 laptops which are much faster. I don't know what mathematical solvers you use or what problems you feed into them so I don't know how much processing power you need.
Mathematicla solvers make a lot of operations. Graphics is not an issue. What they do is millions of calculations, so better performance is whats is required.
Thanks for your advice