Currently using IBM/LENOVO x3550 / 12 GB RAM / 2 x Xeon E5620
What??? This is an overkill for this tiny task.
10GbE uplink currently handling ~2gbps peak traffic.
These services are not meant to sustain 10Gbe for a very long time.
The specs from:
Are pretty good and accurate.
As long you won't use ATOM CPUs you will probably max the 10Gbe.