Here is my scoop on the MacBook Pro.... I prefer my MacBook. If you want extra protection, get Speck's casing (it's a durable plastic that snaps right on the MacBook. I've had my MacBook for close to a year and used it for everything all the time. It has quite a bit of scratches, but no cracks. I bought Speck's case yesterday and wondered where it was earlier, I would have bought it sooner had I known about it, it's great. Also, HDD space.... get an external, really.
I have a M-Audio Firewire 410 interface, I think it's quite good. Only down side is that you are not supposed to hot plug Firewire. So if you absolutely want to be able to hot plug, you'll want a USB, otherwise I'd get a firewire.
Logic Express will let you do 12 channels. That's not quite 16, but close. It's $300. You wouldn't happen to be a student or have a son/daughter that's a student, would you? If you do, you can get Logic Pro for $500, but can't buy the upgrades later on, so you'd be stuck with that version.
The Apple Store (U.S.) - Logic Pro 7.2 Academic
You can also check out Steinberg's Cubase 4, it's $800. Or Cubase 4 Studio for $400, if it does what you need.
Lastly, there is Digidesign's Pro Tools for $250. You'd have to look through them and see which ones do what you want and decide which one you want.
So those are a few options. Feel free to IM me about it if you want, all my IM info is on my profile.