Thanks, pricier than I'd like but the 740 would be an option for sure... Tho maybe I go hunting for another RB5009 again first. While it is not perfect, at least it gets the job done at an affordable price (mine was 225EUR a year ago).
Obviously this is not what OP is looking for, if he's fine with a solution that needs active cooling, he/she would have many different choices, and for 10G I don't think we need DPDK??? Kind of overkill
If form factor isn't a concern, you might think about using Asrock Deskmeet (either AMD/Intel) and replace CPU fan with Noctura, you can then plug a PCI-E 10G dual port.
It's not so much Form factor as power consumption that bothers me about that approach...
Then if you can still find it, the Deskmeet X300 with AMD Athlon 3000G with Noctura L9a could be a good start because this CPU is 35W TDP only, and I saw some people running 3000G/240GE (both 35W TDP) with light loading can have the fan removed when the case is large enough!! (Deskmeet's case has pretty enough room for airflow), then you can plug a desired dual 10G SFP+ card and make it a silent one.
Intel based, you have to find T-series CPU which is hard to get from retail market.
Does have a fan, but uses fairly modern 64bit ARM: Traverse Ten64. They are putting in the work to get it (and other Arm SystemReady boards) supported in OpenWrt https://github.com/openwrt/openwrt/pull/4996 and mainline Linux. Looks like still a bit of work-in-progress here and there, but they have a active forum.
BTW, I just want to tell you that, it's nothing to do with Xeon, with PCI-E 2.0 x4 bandwidth, even you have a Xeon there is no chance to achieve > 14Gbps for a Intel X520-DA2