BGP Router Hardware Suggestions

We are about to discover the joys of upstream BGP routing :-P The
current plan is to use a pair of OpenBSD+bgpd hosts as the routers.

Each host will require 4x10gig ports (SFP+). One of those links
(to AWS) will be close to saturated, along with the downlink to our
switches. The other two will only need to carry ~1Gb/s of traffic.

We are pretty much a Supermicro shop, and I'm wondering if anyone
out there is running a similar setup on SM hardware. My main concern
is finding NICs that will let us squeeze every last drop of bandwidth
on the 10gig links.

I did run some brief ttcp tests on a pair of SM 1Us (don't have the
model number handy, maybe 5018-FTN4s?) with add-in Intel cards
(550s?) and was able to get 700 MBytes/s of throughput. This would
have been circa the 6.7 or 6.8 releases.

I'm hoping to get >70% of the theoretical bandwidth out of the new
hardware, and my gut says it's the NIC that's constraining us.

So, I'd be interested in hearing from anyone running a similar
setup, or who has benchmarked any of the current crop of 10gig NICs
and has good/bad things to say about specific models.

Thanks,

--lyndon