They have it available on Amazon in MP3 format, I just bought the Extra Tracks disc on MP3 and saved to to my flash drive because I have all the other albums but it has some really great stuff from old BBC sessions.
You can buy the whole thing for around $35 I think or just the extras for like $12 but it's worth it in my opinion having some of the older BBC rarities from 1970. Definitely a lot of fun to listen to and hear the original versions of songs they never realeased but would used parts of them on Tresspass, Nursery Cryme and The Lamb.
There's a really early version of 'Anyway' that is called 'Frustration'. It was released on the Extra Tracks disc of the 70-75 box set.
If you like it the extra tracks disc from that set can be purchased on amazon in MP3 format. I got it a while back, didn't want the whole set because I have all the PG albums but I wanted that disk for the rarities on it.
All of them...no seriously. I have yet to come across a Rush album I didn't immediately take to. With this in mind, I would personally suggest Fly by Night, 2112 and Moving Pictures as jump off points. Think about the songs you like most on Chronicles and then find the album(s) containing those songs. Different albums are great for different reasons and some go together quite well (Farewell to Kings and Hemispheres is the example that really pops out). There is also Different Stages Live, a live anthology, similar to Chronicles worth checking out http://www.amazon.com/Different-Stages-Live-Rush/dp/B004JKJQ8Y/ref=sr_1_11?ie=UTF8&qid=1429391868&sr=8-11&keywords=rush+live
Swyncro By Maximum Indifference
LastFM Bio (Band has no official online presence): http://www.last.fm/music/Maximum+Indifference
Official Download Link: http://www.amazon.com/The-Transmutations-Supposed-Angels-Explicit/dp/B0014DK0WA