What speakers would be a good pairing with a Polk LSiM set for a 5.1.4 setup?

The room I'm working on is about 16' x 12' (unfortunately non-uniform as it's part of a "great room"). My old plasma started to die so I replaced it with a nice new 4K OLED LG. Since I now have a nice 4k TV I decided I should upgrade my AVR so for that I got a decent deal on a Denon AVR-X4300h and that seems to be working well. However, some people I respect felt my old consumer level speakers weren't quite as nice as the rest of my system (I agreed) so I started watching for sales. I was originally looking at a Klipsch 5.1.4 setup but I found a good deal on a Polk Audio LSiM 5.0 setup. Two LSiM 705's for the front, an LSiM 706c for the center, and two LSiM 703's for the rear all for $1700 after shipping and tax.

This deal was a bit hard to pass up so I bought them. However, this means that I'm now short the ceiling setup and a sub. I was originally looking at upward firing speakers (thus Klipsch) as the room has a moderately low ceiling (9 feet) and is almost entirely insulated so running cable is going to be difficult. However, in order to pair the speakers properly, I am now considering ceiling mounted as well. I was considering a pair or two of the LSiM 702F/X but without finding them on sale they'll cost me almost as much as the entire set of speakers per pair so that explodes the cost of the setup pretty dramatically and while the $3k for four of them is at the very tip of what I am willing to spend, there's a couple of other components that may need attention first.

I also want to (but from what I'm reading may not need to) pair this system with a nice subwoofer. So I'm curious of two things in this regard. One, for this size of room and given the LSiM 705's do I need a separate sub?  Two, if so, what subs would be a good match?

Finally, should I be worried about getting an amp for these speakers? I've read both that they are power hungry and good with everything so I'm not sure if the Denon is a capable enough amp for them. If it will do for now, should I prioritize a dedicated sub or a dedicated amp first?

I'm only into this system about $3k (good deal on both the receiver and speakers, $5k if you include the TV). I'm not looking to spend that much more (a couple grand) on the system which is where I start to run into problems. After talking to a friend about some of the issues I was working with, he said the people here were friendly and helpful so here I am, asking for some advice.

Additional Information:

I'm using an Xbox One S for my 4k Blu Ray player (please forgive me), I have a home built Media Center PC hooked up via HDMI as well. For SACD I'm using an old Sony dvd player, but I'm considering getting a new one since HDMI will let me use the receiver to decode the DSD. (Any recommendations for a sub $500 SACD player are appreciated. But, as that format is effectively dead I'm not really willing to spend a lot there.)

The system will be used for pretty much everything: gaming, movies, tv, and of course, 2 channel music. Now that I have a decent pair of fronts I'm looking into DSD and high bit rate recordings and players for the Media PC so I can take advantage of them.

My listening habits do not include parties or turning the stereo way up. Instead,  I like high fidelity at low volume. I consistently kept my old Denon at between -42.5 and -35 dB and the new one between 30 and 45 (not shown in decibels, may have to dig through the menu to see if I can show it that way). I am also not a big fan of huge bass, though I do like it when used appropriately (like in Jurassic Park when the T-Rex is approaching the car).

TLDR;

Remaining budget ~$2500

I'm looking for recommendations on ceiling speakers that would pair well with a Polk Audio LSiM 705 set:

I.E. would the 702F/X be worth keeping an eye on to complete a 5.1.4 setup or is there a better choice at a better price point?

Do I need a separate sub in a small room (16'x12') with these fronts, and if so what would you recommend?

Is the Denon AVR X4300h good enough to drive the Polk LSiM 705's or should I use some of the budget on an amp instead?

The budget is for everything (so very tight) so priorities on which pieces you think would help most first are also appreciated.

Thanks;

_WAter_