It would be more helpful to know what you're trying to achieve with upgrade. As far as I know Rotel units are harsh and have tendency to sound thin.
While I agree with presense of great preamp, integrated such as Krell KAV 400i is able to bring more body and refinement to your sound and could've been used as starter instead of Rotel stack. I'd consider Krell as jump-start upgrade to preamp and amp together.
Literally you'll spend less than you've planned after selling Rotel units making your short quick move to Krell.
I like it in all configurations: as preamp only or amp and as amp as whole thing.
Other than that, I'd wait perhaps for larger funds to invest.
While I agree with presense of great preamp, integrated such as Krell KAV 400i is able to bring more body and refinement to your sound and could've been used as starter instead of Rotel stack. I'd consider Krell as jump-start upgrade to preamp and amp together.
Literally you'll spend less than you've planned after selling Rotel units making your short quick move to Krell.
I like it in all configurations: as preamp only or amp and as amp as whole thing.
Other than that, I'd wait perhaps for larger funds to invest.