You're right about the Cisco blade switches only having 1Gbps downlinks, they've not announced anything with 10Gbps ones yet. That said you do have two options, the HP ProCurve 6120XG Blade Switch is 10Gbps all the way as is the HP FlexFabric or Flex-10 interconnects, personally I just love the FlexFabric as it lets you use your NICs as CNAs with FCoE but any of these options are great and all support LACP.
By the way the midplane of a C3/7000 isn't 1Gbps or 10Gbps, in fact it's entirely speed and protocol gnostic, it's just wires - you can throw anything over them so long as the Mezzanine cards and Interconnects match.
Hope this helps.