For a home to smell like spa, you have to scent your home like a spa does. The really nice places use commercial diffusers. But the regular ones often just use the same ones you use at home. The sales person was right, after a while, you get used to the scent and will no longer smell it. And that can happen pretty quickly. All your options sound good but one thing to note is there are different grades of essential oil. The cheaper ones are blended with fillers and that means you probably end up with less than a few percent of the real thing. Most store sell blended concoctions. But it doesn't mean they are out to get you. You are just getting what you pay for. The purer or 100% pure essential oils are super expensive and rightfully so because imagine to get the rose scent, how many tonns of roses must they process in order to make a small batch. They range anywhere from a few hundreds to a few thousands depending on the scent. The purer the oil, the more expensive of course. So I'd say adjust your expectations. Choose an option that you can afford over the long run and be happy enough that your guests will smell it when they come into the house and probably not you.