I think people read a little too much into pr. This has been discussed on the forum many times. PR is just googles representation of the quality of inbound links to your site. It has no real bearing on your rankings.
A good example: I have a site PR5 that ranks #30 for a keyword. The site at #1 for the same keyword has PR1?
PR is great if you want to sell it. But, people are becoming wise to the fact that it is pretty much useless except for maybe giving webmasters a warm fuzzy feeling about how much google may like their site.
You want quality relevant traffic? I would hope so ;oP
So, rankings is what you need. There are 1000's of directories out there to submit to so go ahead and submit to the most relevant. Over time you will build up more and more IBLs and your traffic will increase. You may find your PR will improve as well.
to get into dmoz;
Follow the guidelines to a tee.
Submit ONCE and only ONCE else the editors will more than likely throw your site out for the hell of it. No one likes a directory spammer.
And finally wait and wait and probably wait a bit more. Patience is a virtue when it comes to getting a dmoz listing.
Well for me Dmoz listing is toughest thing for me. Even it is easy to get PR8 but listed in Dmoz is very tough for us. Even I subbmitted a blog to dmoz in Jan. 2007 but there was no updates for me even I get PR4 in last Google PR updates.