I'm a huge amateur when it comes to this stuff (I had a guy hold my hand on the phone and walk me through this) but I use Newsgroupdirect and buy blocks when they go on sale.
Is there a better group to do this from (or cheaper). I'm happy here but I saw an article that had some different places listed and it got me thinking.
if you just want the popular stuff they will be fine since they keep that since many download it but if you veer off that path they have poor completion since their system does not keep everything. but even then with other services at similar prices you can get better for the same price.