You've pretty much got it
As for the second half...
The only really "free server" you're going to find is your ISP... Depending on your ISP you might just be in luck. Verizon outsources to giganews, so their NSP is RIDICULOUS. Cox has great retention these days (something like 70 days worth of files), but speeds are pretty limited.
When talking about the best, that is a tough question. As for the highest quality, Giganews wins hands down. They have the longest retention, highest uptime, and least restrictive rules. Giganews also costs a million dollars. Cheaper alternatives are newshosting.com and usenetserver.com . I've been using newsgroups for almost 4 years now... and I bounce between NH and UNS. I share accounts, and eventually NH catches on, and then we got to UNS for awhile, and vice versa. Most NSP (news service providers) charge monthly, or small discounts if you buy in 3/6/9 month chunks.
To sum it all up, it is going to be the best 15 bucks you've ever spent.