I can supply you Beaglebone Black mini pc in a din rail case for €150 (£130) + VAT, P&P, pre-loaded with OpenRemote Pro 2.5.0, Java 1.6 and JVelbusD.
It will also come with a 12v to 5v voltage dropper for connecting directly to your 12v KNX power supply.
I have developed this unit to support my Velbus customers, but due to OpenRemote's flexibility there is no reason why you can't load your KNX design into it.
Thanks for this proposal.
In fact, the problem is not OR, but the eibd package. The package is now quiet old, and there is some compatibility troubles with librairies, in certain particular cases.
Also, I would give the first preference to use Synology or Q-Nap Nas, as it can be used for other purpose also, without spending time for configuration and so on.