Hartmut,
Assuming you mean practising for yourself to hear only and you don't mind playing with headphones on, may I recommend the Soundcraft Spirit Folio Notepad mixer? Nice flat sound, Line and XLR (hook up your DI) inputs on 4 mono channels, 2 separate stereo in (hook up your CD player!). Only bummer is the external power adapter (bulky and a not so professional plug). I use a Glockenklang Bass Art preamp; both Line Out and DI are completely free of distortion, but I sometimes just plug my bass straight in. You can use your bass in stereo, e.g. to add an effect to either channel (= PU) with Effect Send/Return per channel.
Just plug in your favourite headphones and be amazed by all the details your Alembic has to offer. And the price is no obstacle I guess: Euro 119,= (Musik Produktiv, Ibbenb?ren). Together with e.g. an AKG K141 semi-open, lightweight headphones you'll have a very good sounding & flexible practice setup for less than 200 Euros!
Dass passt, oder?
Take care, Reinier