AMD and Intel CPUs are pointless in this space - you can get far more packet performance, accelerated in hardware, with CPUs like Cavium (MIPS). I happen to work for a company that uses a lot of Cavium processors in it's products and they are the defacto standard in networking gear that is accelerated today. There is a little company called Ubiquiti (not who I'm employed by) has one of the best values in this space for the money. You can buy a $99 router that has a dual-core 500MHz Cavium which will do 1M PPS, oh - and I forgot to mention it runs Vyatta, so hack away.
http://www.ubnt.com/edgemax/edgerouter-lite/
I get it - there are people who want to run soup-to-nuts on a SBC, and there are legitimate use cases. The reality is that Wifi in those platforms is flat out: horrible (again, go buy Ubiquiti UniFi for $80 and get real RF performance - http://www.ubnt.com/unifi/unifi-ap/) Putting an underpowered mPCI card that's sitting around all kinds of other RF noise and likely deployed in the wrong location compared to where your users are anyway isn't ever ideal.
But if you have a hypervisor laying around your house (and 9 times out of 10 on HN that's probably the case) throw your voice at a small instance - or a Raspberry Pi if you're worried about your carbon footprint / electrical bill. There's no shame in that - and at the end of the day you're going to have a far better network in terms of performance and reliability. SBCs are at that weird middle ground of being not worth the money when there's much better hardware targeted at what you're trying to accomplish. They feel, still, very 2005ish to me as they haven't really changed or added value - but the cost is still outrageous for what you get.
At the end of the day don't get caught up in MHz at your router - it's about accelerated packet performance. The Cisco and Juniper's of the world have known this for, well, ever. I have no relation to Ubiquiti what-so-ever other than having purchased a lot of their products over the years for personal use - and the brand is nothing short of undervalued IMO. I'm enthralled that they've branched out from a great line of cheap and reliable RF products to switching, routing, voice, video and even a small nugget of security (although - the L3/L4 firewall of days gone by is nothing more than useless in today's landscape).