I don't use AMR but a couple of things:
1) If you blast a lot to the same sites - especially low quality spammy links/articles - you want to use proxies. This is because maybe 1 in 10 articles to a particular site may get flagged and get your IP banned, having all associated on 1 IP will get ALL your past articles banned at once and keep you form posting new ones. Unfortunately this is especially true on the higher PR/more valuable sites as they tend to have more moderation.
2) If there is any kind of scraping to get your sitelists you want to use proxies, Google is hard to scrape in large amounts, especially over and over without proxies. If there is a built in scrape feature you will want to use it heavily to get fresh and big/high quality lists. The more you scrape the more you're going to need to use proxies for this