Just like the VCR and TV in one, problems are the device with moving parts will break long before the other part does.
So same way, a CD + preamp will not last as long.
I would never get a Cd player packaged into a preamp.
Though some CD players have a volume, and can be used with no preamp in the right setup.
All in one are cheaper, but just have flaws.
So as a long time audiophile, i say do not get a CD player as part of any combination.
The DAc built in a preamp is not a problem(as DACs have no moving parts) . And Cd players have a DAC in them anyway.
it is the moving parts gizmo built into another device which leads to problems.
Just my two ceents.