7es-3 + Line Magnetic vs Vandy Quatro + AR VSI 55?

" I did listen to the LM, and it sounded great, but to my ears the ARC sounded just as good (through a set of Proac D2)."

With respect, which LM you heard should have a some relevance.
That said, synergy is huge and ARC/ProAc is a classic combo. Cheers and enjoy.

@Fjn04, at this particular shop I heard the 501 and the 518. I would like to have heard the Silver series, but they didn't have any in stock, though I know they can order them.

The ARC has unquestionable brand cache and would be very easy to sell if you didn't keep it. Word of mouth says the LM amplifiers really are good sounding(which you've heard and verified) and well built. Sound quality would be my top priority.

You need to listen with your own ears and mind. I've owned entry to mid level Audio Research gear and was never satisfied with the sound. It's smooth and gentle on the ears but I never found the golden tones that I value. More silvery and a little sterile to me.
I paired the gear with Vandersteen 5's and the vsi 55 with I believe Devore Super 8's and Nines. I really did enjoy the Ref amps with Verity Parsifals at a shop in Boston. Still though, they didn't have the warmth I've come to enjoy.

Admirable company, great products, not for me. I should add that I've enjoyed VAC, Luxman, Mastersound amps more. Nver heard of Line Magnetic.

Bjesien
Agree,Good advice,he should listen with his own ears.
Regarding your ARC comments ((I really did enjoy the Ref amps))) Could the difference you heard of possibly been
the Cables you had In your system?
I saw in a prior post you were running Synergistic and Nordost cables.
We found Synergistic to have rolled bass and Nordost
to be lean and clean.
Cheers JohnnyR