Sony Ericsson Mix Walkman phone that looks almost exactly like the SE WT18i (China-only model), so we might see a similar specification in this phone is a 800MHz CPU specifications, HVGA 3.2 inch screen, 3MP camera with VGA @ 24fps video.
For Sony Ericsson txt pro, pro Xperia is similar to that at first glance there but Sony Ericsson's blog post explicitly says second phone is a phone for low end market so of course they are not the same hp. Txt pro and Mix seems to have much in common so most likely the specification is also similar.