Barcelona is expected in the next few months, as AMD clearly indicated that this CPU should be launched by the middle of the year. Everyone suspects Computex. Anyway, Barcelona does not have HyperTransport 3 and it is a server part. Barcelona only supports HyperTransport 2.0.
Budapest on the other hand is AM2+ and it will support HyperTransport 3.0. We mentioned this chip yesterday here.
Barcelona is a socket 1207 part and will fit in Opteron and later in Quad FX boards, including the Asus L1N64-SLI WS motherboard. Budapest should work in AM2+ refreshed boards which supports HyperTransport 3.0.
HyperTransport 3.0 will increase the maximal clock speed from 1.4 GHz to 2.6 GHz and using 32 bit links, it will increase the bandwidth from 22.4 to 41.6 GB/s. So at least on paper it looks significantly faster.
Budapest native quad core is scheduled for late Q3 or Q4 2007.