Is this a reasonable purchase?
No.
You've mentioned your income but not your family's net worth. Unless you are worth a cool $1 million, don't buy a new car; it's never worth it -- building up your savings and investments is a far more worthwhile use of your earnings when you still have a nest egg to build. My general rule of thumb is that the value of your automotive fleet (that is, the actual value of all the cars you own, without regard to any financing, which in general you shouldn't have, even if the terms appear attractive) should not be more than 10% of your net worth or $10,000, whichever is less. I practice what I preach, and then some: I'm worth well north the previously mentioned threshold, and I still don't buy new cars.
There are a number of classic posts on the main blog about how you shouldn't let fear-based marketing (i.e. talking up the latest safety doodads) sucker you into a purchase that will do serious harm to your finances. Read them. An eight year old Camry will still have seatbelts, ABS, front airbags, side airbags (which first hit the market over twenty years ago, by the way), and a grab-bag of other safety goodies. More than enough.
Also, others have said this and I agree completely: Get a second opinion on what your Santa Fe needs and how much it costs. Mechanics can have shockingly divergent views on these sorts of questions. Anecdote: My state requires that used cars be inspected by a licensed inspector (many mechanics carry this license) when they change hands, even in a private sale. I was about to buy my latest car privately from somebody I knew, so I brought it to a local shop to have it inspected. They came up with a dozen alleged points of failure and a several thousand dollar estimate to repair everything. Some of their points of failure were, shall we say, a touch "aggressive" to my moderately experienced shade-tree-DIY eye. Accordingly, a few days later I brought the car to a second well-reviewed shop to have it inspected; lo-and-behold, it emerged with two points of failure which cost something like $50 or $100, total, to fix. It's given me thousand of miles of safe and reliable service since. So let me repeat myself: get a second opinion and possibly a third opinion on the Santa Fe (if three mechanics all agree on something, I wouldn't push the point further). I wouldn't be surprised if your repair bill falls by 60% or more and you suddenly don't see the need to replace that car just yet.
TL;DR: Don't buy the new Civic. Get a second (and maybe third) opinion on fixing your current Santa Fe. When the time finally comes to replace a car in your fleet, buy a used, 7-8 year old full sized sedan.