Have you tried the at-home techniques first? You can get pretty darn good results with it! I am a smoker and drink coffee and wine, so my teeth were getting a bit yellowish.
I'm doing the strip method now, but not Crest since we don't get that brand here, but I tried the Crest ones before in Canada. I'm using a brand called Odol, and I find it better than the Crest whitestrips because the material is more grippy so it molds to your teeth better and stays in place. It's stronger too, I think. I've only been doing it for like a few days so far and I'm already noticing results! Last time I did it a lot of people complimented how nice my teeth looked.
I'd try some of those at-home products first and see what works, I think getting it done professionally is really expensive.