Hello,
price without USB interface is lower little bit. But we highly recommend to buy USB interface if it is your first Spirit unit.
For connection with HoTT receiver you can use this guide:
https://manual.spirit-system.com/index. ... upner_SUMDFor HoTT radio we recommend also to buy HoTT integration cable.
It can be connected according this guide:
https://manual.spirit-system.com/index. ... ntegrationBluetooth module can be easier for operation but it can be used only with Android devices.
Wifi-Link can be used with all devices, including a computer and smartphones and there are more possibilities.