Do you raytrace render on the laptop or just use the preview window?
if you raytrace, core i7. if you don't core i5 will be just fine (as the load is on the GPU).
Pick a brand you like, a product you think sounds right (8+GB RAM/64bit OS) and post a link here. We then can see if you it has a REAL GPU, not some CPU/mobo trickery.