I'm a big fan of console safes. They are expensive - in the $250-$300 range - but they are more secure than most lock boxes that will fit under a seat, even if you bolt the box to the floor. And they hold a lot more stuff.
I bought my most recent one from Console Vault, and like most console safes it is made for my specific vehicle and bolts to the vehicle. If a thief had enough time he could probably pry it open, but I doubt he'd be able to pry it out.
Any vehicle safe is a two step approach to security. While it is entirely out of sight, a thief will obviously look in the console if he breaks into your vehicle. However, those efforts are usually very quick smash and grab efforts, and if there is nothing visible in the vehicle worth stealing in the first place, a thief will choose another target that is a sure thing. If he does choose your car, he's now faced with the problem of any knowing if anything is in it (he can't shake it, or feel the weight of it), and it'll take both tools and time to break into it - and he may be very short on both.
Console safes vary a bit by model, and they do reduce the internal volume of most consoles, but there is still usually lots of room. In my case (Toyota Tacoma) there is also space left between the vault and console lid for sunglasses, and other small items.
There's ample space inside and the alcove on the side works well for a box of ammo and/or spare magazines.
After a box of ammo, 2 spare magazines, a pair of speed loaders, and ear plugs, I have room for my 2.5" Model 66 (in my 3" Model 13 holster, along with my 6906, and I still have room for my CZ 2075.
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If you go the lock box route, it works best if you can bolt it under the seat, but that either requires a model that slides out of a tray bolted to the floor, or it requires a seat that slides back far enough to allow you to open the safe.
If neither of those options work, then the cable they come with is better than nothing. But it's a cable that isn't had to cut with a small pair of bolt or cable cutters. So it will be far more effective if you ensure both the box and cable are indeed out of sight, and there is nothing else visible in the car that would encourage a break in.