Excellent! The crawler does get CPU bound so having multiple machines (and/or cores) makes it go faster. We (as in Blekko) also maintain a list which we call the "crawl frontier" which are pages we know about but haven't seen enough relevant data about to decide whether or not they are "worth" crawling. Although some new stuff we just built will help with that.
Much of what we crawl is shared with the common crawl folks so that can help you with your choosing perhaps. Also that corpus provides a good way to test indexing and ranking algorithms. Things I like to test are queries like "Who are the Cardinals?" which can catch both sports references (Arizona and St Louis Cardinals) and church references (Pope Francis just named/blessed/appointed a bunch of new Cardinals). Often times news sources or blogs can help identify which interpretation of an ambiguous word is probably more relevant at the moment.