Just can't find any going for under 600SGD on Newegg. Cheapest I could find was the Dell S2417DG, but it's QHD. Should I go with that, or are there any better options?
QHD is definitely better visual quality than FHD, but as I said before it's hard to say which would be better for you if you don't tell us your other specs.
You are looking at a 24" monitor? You are wanting 4k? Personally I have a 27" QHD G-sync as I think that 4k is really only worth the money for larger monitors. And you will need a GTX1080ti at least to run it.
QHD is definitely better visual quality than FHD, but as I said before it's hard to say which would be better for you if you don't tell us your other specs.