if you're planning on sitting in the saddle for 100 miles at a time, and you're anything like me (i.e. not going to do those 100 miles in less than 5 hours, for an example), you're not going to like my advice.
if i had it to do all over again, i would spend the extra money on a brooks tensioned leather saddle. after a good fit and fatter, lower-pressure tires, there's nothing that's going to contribute more to the comfort of your (presumably long) ride than a good saddle, and it's a thing i wouldn't skimp on. i'd rather spend less on the frame and wheels.
to summarize: i have no idea what kind of decent touring saddles are available on the cheap (new), and don't have a good answer to your question.