I would certainly not recommend a sound bar. Conventional wisdom says you should always go with separates (receiver and speakers). You can purchase nice HTiB's at your price point (receiver/speaker combination in a single package), but the speakers are usually the weak link. Good speakers can make a mediocre receiver sound great, but mediocre speakers can make a great receiver sound bad.
Wireless is an option but most wireless systems still require a power outlet for the back speakers and both of those speakers are usually wired together. The wireless part means that you don't have any wires connecting the back speakers to the receiver. There are systems that have powered transceivers so that the speakers don't need to be wired together, and there are other options as well but it can get expensive and you are always left with the possibility of problems due to the wireless technology. Wireless can work very well but you need to do your homework and audition them if possible.
If your new tv is 4k with HDMI 2.0 input(s) then you'd be best to look for a receiver with HDMI 2.0/HDCP 2.2, at least 4 HDMI inputs, and any other bells and whistles you think you'll need/want. Most higher end receivers from Yamaha, Denon, and Onkyo will have everything you'll probably need for the near future.
Speakers can be tough depending on what you want. Floor standing, bookshelf, 5.1 or 7.1, one or two subs, etc. Size of the room, configuration of the room, furnishings, etc will have a definite affect on your sound. It is really a good idea if you can audition the speakers first to see (hear) if they sound good to you. But keep in mind that where you hear them will be a bit different than in your own environment.
So, what to do? I would look for a receiver first. Once you decide on that, or have a good idea of what you want, then I'd go to the speakers forum, state the receiver you want, how much you want to spend on speakers, your needs, and see what they say there. If you go the HTiB route, I would not get an integrated system (one with a built-in blu-ray player). Sub-woofers are usually passive and you're limited somewhat in options and upgradeability.