I decided I would take things a little further and poke around with haproxy some more. The initial plan was to compile the latest dev source of haproxy with SSL termination enabled.
In doing so I realised I would lose SPDY support, which upset me a little. After some digging I found that the 1.5-dev branch of haproxy supports npn and thus can handle SPDY.
I tweaked my builds a little more and managed to get haproxy running as an SSL terminating load balancer, with SPDY connections being sent off to my nginx servers with SPDY enabled and all other non-SPDY connections were passed on to an nginx virtual host with SPDY disabled.
I have released my haproxy build as a debian file below …