I really dont think anyone knows what would happen if you submitted to 2000 PR0 sites, eg would you get PR1, i asked this question before and got no answer that I was happy with.
Really except for the google programmers there will be few people who have the knowledge to answer the question but think of it like this.
Google wouldnt take a point off you for listing on non related sites, becase for you all you know there are people talking about your site on a womens chat site, so that would count as negative feedback. + it would open up the possibility for your competition to go around submitting your link to un related places.
As per googles info, you get a vote when a person links to your site, now maby you get 1 vote for a link, and 100 votes for a link from a pr4 who knows, but its a vote none the less.
Also, I cant imagine that google would make it so that the people with the biggest pockets gets to the top of the SERPS, because that would mean big companies would get a monoppoly on any market they wanted, just throw 2 mill at SEO and youd be at the top, there has to be a component of no users auctually using your site, and or links that are not paid for. This becomes more plausable when you look at what the google analytics records.
+ there are people who have like 150,000 thousand posts on a forum, so I cant even imagine how much it would cost to buy 150,000 backlinks (real links) + im sure these people have other forums they use, so that has to count for something.
I would just take some time to work out what sites are relevant to yours, and what you can do for them in return for a one way back link to your site. Help moderate their forums, write in their blogs, etc etc, but at the end of the day its prob easier to earn $500 in the real world mowing your grannies lawns, then spending that money on SEO than it will ever be to get enough backlinks to to be equal to $500.