serp ranking and pagerank are different concepts
yahoo may cost more than it is worth
you can try dmoz, they are free
www.bluefind.com = $50
www.sevenseek.com = $40
www.incrawler.com = $25
most directories charging a one time fee are not offering PR6 or PR7 links...that was an untapped market position until recently. usually for links of that PageRank you either need to deserve them or rent them.