Depends on your area, many places internal aerial is not sufficient. You cannot use OEM aerial+amplifier as the amplifier only amplifies AM/FM frequency range and filters the rest out so most of DAB will not work. In the A6 I removed amplifier and connected existing cable straight to the aerial. With the amplifier there was no DAB reception at all, without it it's acceptable in the area I live in but it does loose signal in many places around the country but OEM aerial without amp is still better than 2 cheap glass mounted aerials one of which was passive, other amplified. FM radio is also still connected to the OEM aerial and reception is slightly worse than with OEM amp. For best results quality roof mounted amplified aerial something like this
https://www.dabonwheels.co.uk/product/jvc-hal-2/ is needed but they are not cheap and I don't really fancy laying cabling and drilling hole in roof so it will do for me as in my area it's good enough.