Marantz receiver questions

I have a Marantz PM7001 that I'm perfectly happy with, but the speaker wire connections have gotten so sensitive that the speakers often cut out and I have to tinker with the wires to get the sound back.  I tried cleaning--nothing doing.  Worth taking into the shop or time for a new receiver?

I am playing classical and jazz on cds--Marantz CD6006, Paradigm phantoms.  Will I, a non-audiophile, notice sound difference between the PM6007 and the PM8006--worth the nearly 1K Canadian difference?