For what you will be doing, although I love my MBP, you will NOT need that power.
I know you said you don't want to keep disconnecting things, but really all you would have to do is connect the monitor and one USB (get a 10 dollar multi usb plug to keep your keyboard and mouse stuff and anything else.. like external harddrives in) and it doesn't take any more setting or anything. As soon as you connect the monitor it will show up and work. It takes 5 seconds to plug those two cables in when I come home. Less then if you had to start up an imac after a trip. It's not much of a problem at all. And since you won't be traveling THAT much it shouldn't be a problem at all.
If I were you I would go with a basic midrange macbook and a decent external. You don't have to get an apple display. It seems like you aren't concerned too much about color accuracy or printing, so a nice samsung or I even have an acer which is really nice for the cost will do you well.
The MBP you'd look at would be about 2200
The iMac is like 1800 before tax.
You could get a macbook for 1300 (mid range white) and add on a nice 22inch monitor for 300 (my acer was only 180) and that is only 1600! Add on a nice external mouse and keyboard for 50 and that's 1650 for a full set up which is the best of both worlds! You can now get a 2gig stick of ram for like 40 bucks from places so that's less then 1700 before tax for a super fast portable that makes a great desktop.
The macbook is more then enough for what you need it for, and will surely make you happy. For working in coffee shops etc, the screen should be AOK for you, do intensive work at your home. I really think this would be the best option.
If you want till January for updates you may even get a better deal on something. The new macbooks should be in refurb store by then, so that should save you yet another 100 or 200 dollars!
Otherwise, I'd go with a refurb 2.2 macbook pro. You won't need anything more powerful then that. It flies for my 3d rendering even.
Just my 2 cents