I`m sure, the DAB tuner will work with your BS2300. It will be controlled via Datalink of the AUX socket. Just the same way as with a BC9500. Do you have the "early" BS2300 with two-way communicatio?
Should also be possible to split the AUX socket and use the input for the tuner, incl. Datalink and the output for your external amps. It`s a fixed line level output. If you have non beo active speakers directly connected to your BS, use Powerlink output, because it`s a volume controlled line level output that is required by a poweramp input. You can even power up/down your active speakers by a trigger signal via Powerlink - if your active speakers are supporting this feature...
More information about wiring of AUX and Powerlink plug:
http://www.beoworld.org/beotech/misc2.htm#Audio%20Aux%20Link%20/%20PowerLink%20connections:
Hope this helps
Stefan