Deep Purple Remasters: Machine head/Live in Japan

While I would not call them audiophile classics, they are much improved from the original releases. Who Do We Think We Are! also sounds very good, but I hear less improvement on the Fireball and In Rock remasters (In Rock is only available on import for some reason). Note that I think all were de-noised if that is going to bother you. Bonus material and packaging/notes on all these releases makes them worthwhile if you are a fan.

There was a DCC Gold version of Made In Japan that is supposed to be very good, but I have not heard it.

I own both the Rhino and DCC gold editions of "Made in Japan," and if you can swing it, the DCC is the one to get. It's not a mind-altering difference, but the gold sounds more open and detailed.

I have a copy of Machine Head with a remastered disk and one remixed by Roger Glover.
The quality on this Rhino release is very good.
Also includes a few other tracks not on the original and Quadrophonc mixes for Maybe Im a Leo and Lazy.