I've recently bought some slightly left field box sets. Not left field in terms of artists, but in terms of period. One is Fleetwood Mac, Original Album Series. This is about 1970-74, so it is the end of the Peter Green period but pre Buckingham and Rumours. Christine McVie comes along half way through and you can hear the change. It's fascinating, and a period few people know. We all know Albatross and the bluesy stuff, everyone in the world has at least one copy of Rumours (cue somebody with his nose in the air trying to be superior saying "no, I've never owned Rumours. Or DSOTM. Or Born in the USA..." ) but who do you know who owns and plays "Bare Trees"?
This box has Bare Trees, Kiln House, Future Games, Then Play On, and Mystery to Me. The only album it lacks from this period is Penguin, which I recommend you buy seperately if you don't already own it. It's a great album, probably the best of this period.
Also in "Original Album Series" is some Jethro Tull. Again, I know, we all have Aqualung, but who's got Stormwatch? Maybe nobody needs a copy of Broadsword and the Beast. It's worth a go for £11 for 5 albums, at the very least you will hear stuff that you haven't heard before and that never gets played on the radio. Is it their best work? No, but you can hear where they come from and where they are going. It still won't make me rush to get out my copy of Crest of a Knave, but there you are.