I feel like I've seen the 27inch version of that Dell go on sale for nearly 500. Maybe wait until Black Friday?
If that's all you want, you can pay a lot less.
First off: what kind of games do you play? Your priorities will depend highly on that.
Also, what kind of GPU are you running?
Yeah I think the S27 gets close to 550 give or take. But iirc, the 24 has better QC, DPI, etc. Then again, it's dell, good return/exchange, etc etc.
All types of games. I have a i7700k 4.5 ssd 1 gig and 1060 3gb
S2417DG then; but if you really want to stick with 1080, get a non *sync monitor with 120/144hz, and use the leftover money for a GPU upgrade next year.
But if you get the s24 when it's on sale, you'll be set for a while anyway; you'd just need the occasional GPU upgrade without having to worry about buying a new monitor for quite some time.
edit - let me get this out of the way first, if you know someone that has a high refresh rate monitor or a gsync monitor, play some games on it and see if it's worth spending the extra money.