Look at eBay for a week or two and that will give a general idea of what prices are being achieved by ordinary members of the public selling their unwanted B&O kit.
Prices have dropped lately so I would be surprised if you achieved much more than £300 for the 2300 alone or £575 with 2500 speakers.
Do not be mislead by the higher prices being asked by the likes of Lifestyle-AV/MorethanAV/Iconic-AV and Beo4life, as these are their asking prices and not the prices that they actually sell for. Established resellers who offer additional services including warranties and their good name do however charge more and with with some justification.