Have you though about having the existing tub resurfaced? There are some pretty good products out there (applied by appropriately skilled peolpe) that would rejuvenate your existing tub without the expense/hassle of replacing it. They use a spray on ceramic type coating that can potentially last for years and you can choose a colour that will match your new decor. I myself haven't had this done, but have seen others who have. It won't last as long as a new tub ( maybe 5-10yrs) but the results are pretty good within this time frame. Just don't have your whole bathroom resprayed with this gear, the guys out there doing it tend to go over the existing grout and all, which looks a little ordinary!