I have the SDS-470C and it has been great for the past several years. I would not use it with really sensitive speakers though as it is a bit noisy...not an issue with the Elacs.
I would also not use any of the Class D Audio amps with a passive pre since they need gain to come to life due to low sensitivity (2V input) and low input impedence. IMHO, the amp would not be a good match for that system.
Indeed, for a portable system I think going with a pair of active speakers would be a better solution. Especially something with a built-in dac like the KEF LSX or LS50W.