Depends on how much extra money the T9300 is. If it's a $100 upgrade (as in the Lenovo T61P), then by all means go for it. If it's a $300 upgrade (as in the case of some Dell XPS laptops), then no, the 10-15% performance gain is not worth an extra $300. In gaming, most of the work is done by the graphics processor (unless you game at a very low res like 640x480), so the CPU has little effect on performance in comparison to the graphics unit.