I agree with Zumbo. Buy as much as you can as long as you can. You'll have this thing for a long time, and wishing you would have gone a little more. I always tell people when buying a house, buy way more than you can afford. 5 years later you won't be sorry when you're making more money and in a better neighborhood. I bought more than I could afford, and now I wish I would have gone even bigger. As far as buying online - it's nice to have a little bit of a warranty, even 30-90 days. If the unit runs for 2 months, you are usually safe. If you had to send in the unit for a major repair, figure $100 in labor/shipping and $100 in parts. If you'll save more than that, buy online. If not, get it locally.