All-in-one systems are ideal for those who want to get a decent quality of music at a relatively affordable price or perhaps have no choice due to serious space constraints.
I personally prefer separates as I view these as 'real hi-fi' - that's just my view. It also provides me the option to mix and match, upgrade, downgrade etc.
The CS515 is reported to offer budget separates a good run for the money, which is admirable, and that reflects how far ahead these components have come in terms of sound quality.
At the end of the day, the choice is yours.