You mentioned 23x24" so I'm guessing width isn't a constraining factor.
Phanteks P600S (20.5" height, 20.1" length/depth, 9.5" width) will give you better GPU results and if you decide to upgrade or expand your system it has support for 140mm fans at the top (as well as support or 280mm or 360mm radiator ; 190mm CPU cooler clearance). The biggest complaint people have had with it is the 24-pin ATX connector interaction with the sliding plates that they use instead of cable grommets. If I had to add to that list it would probably be the lack of any secure fastening method besides magnets for the side panels that swing open.
P400A (18.3" height, 18.5" length, 8.3" width) is an option with 420mm
GPU clearance (i.e. even if you subtract 60mm for some clearance from front mount radiator you will have space) if you can't tolerate the P600S size (keeping in mind it is using the budget Metallicgear Skiron fan) . There's some design concessions to hit the price point: for example the panels are slotted into the side similar to other budget cases , putting the TG panel on requires 4 thumbscrews , 3.5" drive bays are plastic. It's better than H510 because H510 is vented only on one side + bottom but you lose USB 3.1 gen 2 type C at the IO (it's a budget case at its core).
The Meshify S2 (18.3" height, ~21.2" length, ~9.2" width) can mount the radiator in the top but since you have an air cooled GPU it wouldn't make as large a difference. It supports 140mm fans in the top (most cases that support 140mm fans in top also have higher CPU cooler clearance, this has 185mm) and up to 360mm radiators in the top unobstructed / 420mm radiator with 35mm motherboard component height. The fans are weaker than the ones in the P600S.