Moya,
You can do it with or without the PBX. Use Quintum it will generate the CDR’s for you through their CDR Server software shipped with the gateway. If you buy Quintum used you may not get the latest release and the cDR server software. Very limited.. Suggest using a billing platform if you intend to do serious billing while using a RADIUS Server. You can not do Radius and the cdr server together it’s one or the other. I have infomration describing the pbx setup if need be, but sounds like extra equipment you don’t need
Any further questions let me know
Dave