My friend swears by giganews and downloads more than me....the Verizon servers I use are so good that I don't need a 3rd party provider myself but you should be good to go with giganews I think.
I hear the rates are $16/month for 12GB worth of bandwidth so that doesn't sound to bad either...
Finally try your luck with Newzbot at
http://www.newzbot.com which is a list of public NNTP servers, it's probably not quite what you're looking for but it could come in handy for fills or old files, obscure groups, etc....I used to use it all the time