Warthur
Of all the three Rush "Sector" boxed sets - each containing four studio albums plus a live album summing up the era in question - Sector 2 is probably the most essential one. Sure, Sector 1 might have the almighty 2112, but it's also got a bunch of significantly rougher material from when Rush were still polishing their sound. Sector 3 covers their synth era nicely, but that era got decidedly patchy towards the end.
Sector 2, though? You've got three classic albums (A Farewell To Kings, Permanent Waves, and Moving Pictures), a patchier one (the rump-tastic Hemispheres, though I know some people really love it), and perhaps their all-time best live album in the form of Exit... Stage Left. What's not to love? (There's also a DVD version of Farewell To Kings to sweeten the deal.)