Lenovo's Thinkpad line still has 15" widescreens with 1920x1200.

My personal mailbox is 1.3G on the server, and my work mailbox is 2.7G on the server. Both are accessed via IMAPS. Neither seems to register any significant CPU utilization. Additionally, since I run both clients simultaneously, one would think I'd see even worse performance, but I don't.

I run two instances of Thunderbird 3.0 here, with two separate profiles (personal and work). Overall, my CPU 96% idle at most times. that's even with Chrome and Opera sessions open. More often I find that Opera's plugin wrapper freaks out and wildly thrashes on one of my cores. Can't say I've ever seen Thunderbird consume huge amounts of CPU time other than when I've asked it to do some massive operation (some operation on hundreds to thousands of e-mails). Even searching my entire mailbox (personal or work) doesn't cause it to consume much if any CPU time.

Firewall Builder does most of what the submitter is looking for already.

Time Machine alone is a huge reason to upgrade. Sure similar results can be had with shell scripting, but it really isn't nearly the same experience.