The Store by default shows them in reverse date order - newest on top - but you can change the view by clicking on the column headers. When subscribing the iTunes application shows them in reverse data order and this can't be changed, except by using the recently introduced 'itunes:order' - I don't know whether SoundCloud supports this tag.
I quote from http://www.apple.com/itunes/podcasts/specs.html
The <itunes:order> tag can be used to override the default ordering of episodes on the iTunes Store by populating it with the number value in which you would like the episode to appear. For example, if you would like an <item> to appear as the first episode of the podcast, you would populate the <itunes:order> tag with “1.” If conflicting order values are present in multiple episodes, the store will order by <pubDate>.
I can't comment further without being able to look at the feed.