Hello @culkinad. You can handle more 2000 customers and on desktop HW like (i5/i7 ivy-bridge). Main HW params in this case NIC intel 82599 or x710/xl710. As for servers HW - nice choice PowerEdge R640. Also you need to disable HT and enable RPS, because PPPoE is L2 traffic. Of course CPU and RAM frequency have matter.
Hello @culkinad
For perfomance with 2000 pppoe clients we recommend you use CPU with higher frequency. And Intel network cards.
The processing speed of packets on the network will depend on the processor frequency.
Depends on your budget.