For home practice, it is possible to play a digital organ module without connecting it to loudspeakers. Use a professional audio headphone instead, if you don't want to invest in a set of louspeakers with subwoofer. In the past, I paid about US$147 for a very durable Austrian-made 600-ohms K240 AKG Monitor headset. For this amount, you'll be able to hear the full spectrum of the audio output from 16hz to 24khz of the organ module. The headset is now over 11 years old and is still working in excellent condition.
The only setback of using a headphone for practice is that some of the lower harmonics appear to be more thinly expressed than what would have come from the loudspeakers, while you could say this promotes clarity of the audio, giving a more discerning refinement of the audio output as a whole. Another is that wearing a headset over two to three hours could cause pain to the ear lobes.
Remember, the organ module works quite differently from your mini-Hi-fi system with regards to the way their earphone outputs work. Ordinary Hi-fi systems would cut out any audio output to the loudspeakers the moment you insert the headphone jack into the socket. But the sound modules, at least those I own, don't work in this way. The two outputs are independent and can work at the same time -- so you could listen with your headphone on, while the outputs to the loudspeakers remain unaffected.
Today's K240 MKII Headphones, Semi-Open, Dynamic, boasts capability of expression of 15Hz-25kHz:
