Any thoughts on why the 500 and 1000ksps versions exist as there is essentially no apparent benefit in sampling quicker??
If your project needs to avoid aliasing noise and images, it needs very wide gap between antialiasing LPF cut-off and Nyquist border (Fs/2). This gap allows to place LPF slope where rejection is not good.
This is why recommended sample rate is 10-20x times higher than AA LPF cut-off.
So, if your LPF cut-off is 15 kHz, then recommended ADC sample rate is 150-300 kHz.
But there is also another issue, since analog LPF has bad flatness near cut-off, it's better to use LPF with 2-3 times higher cut-off to get good flatness and then apply LPF in digital domain to get almost ideal flatness. In your case it means that for 15 kHz working bandwidth you're needs to use analog LPF with 30-50 kHz cut-off and about 600-1000 kHz sample rate. In that way you can get high out of band noise/image rejection, the best flatness and linear phase within required 15 kHz bandwidth with using high order FIR LPF which has almost ideal flatness, very sharp cut-off slope and high 100-150 dB rejection in bandstop region.
But it depends on your needs, do you really needs very good filtering and ideal flatness?
If so, then these expensive solutions are worth the effort.
Good quality high dynamic range signal requires expensive components and large computation resources which is also expensive. So, the quality needs to pay more money.