Boxes that you ship are going to get the same sort of crappy treatment whether they're luggage or if they're going via some standard shipping carrier. The big advantage offered by taking it on the plane is that you theoretically minimize the # of stops that your package will make, which I think would minimize the chances for it to be mishandled and/or tampered with.

I think you will be way better off with this option. I did a cross country move many years ago, and never even considered this. I only had a small # of items, and they were shipped across the continental US, and I know I paid at least as much as replacement items would've cost. I'm sure shipping to HI would be even worse. This was before craigslist/freecycle, so it wasn't as easy to get rid of stuff locally

For the printer, you might be better off to ditch it and buy a new one there. In many cases, it's cheaper to buy a new printer than it is to buy replacement ink for an old one. If you have a more expensive printer where that's not an option, make sure to go to the manufacturer's site and see if they have any suggestions about prepping your item to be shipped. They might suggest removing toner/ink carts & sealing them separately.

For the speakers, take a look on newegg.com to see what new ones would cost. If you just have basic speakers, it's probably not worth shipping them.