70’s rock pressings. Witch equipment deserve?

...feed the output to a pair of Crown amps to JBLs'....

Listen to it with what made it sound great 'then'. :)

Absolutely, it’s worth it. Gobs of amazing sounding masterpieces from that era. The MOFI / Nautilus / Half Speed / Direct to Disc / etc pressings aren’t necessary. Heck, I have lot of heavy metal 80’s - 2010’s on vinyl that sounds great! If a system only sounds great on Krall, Barber, Lyn Stanley etc (and I’d be suicidal after an hour of listening to that fare) - then it’s an unbalanced hot mess of a system, regardless of what the price tag and seller says.

There are many great things for you to discover, like how Dire Straits is FAR from the only rock band that sounds excellent on vinyl. 

but I’ve only heard one (a limited edition something or other) with an SME V arm and that will suck the life out of any deck.

Very interesting - that was my exact feeling about this much revered arm. I kept my opinions to myself lest I be outed as a cloth eared cretin. Peerless in some departments, but very boring, as it cannot convey rhythmic information with any conviction.

Pay Gentle Giant, et al the respect they deserve and get the best your budget can endure. Add some atmosphere -an open fire, big old chairs, a few crusty old friends and maybe a little Ganja. Its what prog rock was made for.

Had a really interesting experience way back when a friend brought over a MFSL half speed mastered pressing of Sticky Fingers. 
 
We waited with baited breath for the stylus to hit the vinyl to be finally rewarded by ...,
A very flat, bland and totally uninvolving sound.

Upon reaching for my well played early English pressing (complete with real zipper!) we were rewarded with a ballsy dynamic sound just bursting with life and energy. The difference was not subtle. 

The moral: not all vintage rock vinyl sucks.
And if you can, try before you buy.
Or maybe it was just the zipper?