Hi,
I see. Personally, I would recommend this appliance for your scenario, as it fits the bill, is tested and known to work with IPFire perfectly, and future-proof.
(Disclaimer: I am not affiliated with the company selling it. 
)
This question has been discussed multiple times. Please refer to threads such as this one for further information on combining IPFire and PiHole.
Thanks, and best regards,
Peter Müller