I think the CPU will not be the bottleneck in gaming paired with an X1400. You should be fine in all other respects. I believe there is around a 15-16% average performance difference between chips of the same speed rating going from Core Duo to Core 2 Duo. According to a Google search, the T5200 has a 533Mhz bus speed, and the T5500 has a 667MHz bus speed. I think no matter what you choose, from the laptops you're looking at, you'll be happy for a while; these are all pretty powerful. My Thinkpad T60 has a Core Duo 2GHz, but much of the time I can't tell a lot of difference vs. my last Thinkpad, a T41 Centrino 1.6GHz.
You don't need a small business account-- you just need to submit an order through the small business portion of the site at Dell. The D620 is an awesome laptop, although I read initially that some people were not getting great gaming performance issues with it due to problems using a non-business driver (but I stopped tracking the issue and hopefully someone who owns it will weigh in). The X1400 will beat the NVidia chip in the D620, but I think the D620 is a great laptop.
Happy holidays!
You don't need a small business account-- you just need to submit an order through the small business portion of the site at Dell. The D620 is an awesome laptop, although I read initially that some people were not getting great gaming performance issues with it due to problems using a non-business driver (but I stopped tracking the issue and hopefully someone who owns it will weigh in). The X1400 will beat the NVidia chip in the D620, but I think the D620 is a great laptop.
Happy holidays!