Why don't you automate this process? All of the people you upvote have the most credibility, the posts they upvote have a little less, and people who upvote those posts gain a little credibility too, and so on. Tuned right, voting itself becomes a function of whatever the base of the community is.
New users -- depending on what kind of posts they upvote and who upvotes their posts -- must be able to gain credibility quickly, not just by upvoting the top posts, but picking winning and losing comments in the long term.
I think a method like this is necessary, as I really don't think you could determine post quality with an algorithm itself. You can't automate that type of intelligence.
Given HN's current latency, though, you'd need a few orders of magnitude more resources.