You're spending most of your day in this chair. It's better to buy one quality piece that lasts years than to replace a cheap one every twelve months.
Keep an eye on when manufacturers drop new models. You can often snag last year's version for much less during back-to-school or spring sales.
Keep in mind that the 0% intro APR for 15 months on purchases and balance transfers is a deadline, not free money. If you haven't paid it off by the end of the period, you'll start paying interest on the remaining balance.