Congratulations on your new job! Sounds like you are ready to get busy in TMMTX for the new truck soon...
The regular leather is pretty nice! I really like the Lexus leather. Unlike the American or the European cars that their leather tend to be a bit harder, the Lexus leather is very soft. I mean, it feels like a high end Italian sofa! I don't think the perforated seats are that much difference besides the cooling and heating capabilities. Whatever you choose, you will not regret with Lexus leather. The only thing I am concerning is that regular seats don't come with heaters, so your buttom might not like it in the winter. :-)
I think the Halogen is ok, but of course, you should get the HID, there are many aftermarket companies that make them. You should check on the forum, many people had already talked about it.
My personal pick would be IS 350 w/: rear spoiler, HID, 18" wheels. X-package is not worth it, you don't even get a rear spoiler and the sport tuned suspension is stiff. I mean, it is not super stiff like the EVO but it is stiff by Lexus standard, you might not like it if you plan to keep the car for a while.