To try and help a little here, I will address the proxy question first.
Because of the shear volume of posting/commenting that will occur as well as the scraping and harvesting activity, rotating through a single IP address with your ISP will ultimately result in almost an immediate blacklist from Google and many of the other blog hosts. In my opinion, you should invest in some Private proxies (10 should do it) for your scraping and harvesting activities. For the actual posting of comments, I would recommend using highly anonymous proxies, such as the ones found here on BHW or by scraping them yourself. This will result in your commenting being anonymous.
You should consider that you will be most likely commenting on thousands of blogs in one session, so it should be clear that the proxies are a MUST.
Regarding the question of whether Scrapebox is worth it or not depends on what you want to accomplish. If you want to build backlinks to your Tier1 and Tier2 properties, then the answer is absolutey it is worth it.
I would highly recommend the product as it is a necessity for serious SEO.
Hope that helps.