SPDY requires that you run it inside TLS. Within the already existing TLS handshake the client and server can advertise that they support SPDY instead of HTTP.

The way you describe it comes of as more complicated?!

Of the things to note is that nothing of SPDY describes encryption, which is why a lot of people have thought about using it without TLS via some other negotiation strategy (but nobody have really implemented this, since the value is only minor/non-existent outside internal networks).