If your were to assemble a vintage system ?

All of the above bought used over the past five years. Only the custom SUT was new. Best bang-for-the-buck by shopping on the secondhand market!

1. Advent 300 receiver
2. Large Advent (walnut) loudspeakers

3. Dual 510 turntable w/Micro Acoustics phono cartridge

I've got a vintage system that includes a Thorens turntable from 1985 - TD 166 mk2 mated to a Sumiko blue point #2 cartridge. But I never understood why audiophiles use the term "musical" to describe the sound of a certain hi-fi component when music is what they play over their system. I mean, doesn't it all sound "musical?"

I would acquire a Quad 405 amp and a Quad 33 preamp, then rebuild them and add the DC/delay option offered by Dada.  For a turntable, a Technics SL-7 and some P-mount Ortofon cartridge or a Thorens TD-150 or the like and an Ortofon M2 Blue.  Speakers are a challenge.  The budget would probably not allow AR-LST's, but maybe AR-3a's or that failing, Dynaco A-25's.  I'd make my own cables as I have always done.Note: I have done the amp and preamp rebuilds and they perform very well in my current system.

This is right in the wheelhouse of our little shop here in Austin. We restore pre 1980 amps, receivers, and turntables for clients. And in our mind, "vintage" ends around 1980.  A few suggestions.

First, any vintage amplifier or receiver should have recently replaced electrolytic capacitors. It’s a waste of time otherwise. No doubt the reason that some have had bad experiences with period gear. You won’t hear it as intended otherwise.

Some speakers age better than others. Classic Klipsch usually need little or no attention, many other mid centuries use foam surround and NPE capacitors that need replacing.

Unless vintage cart has a new (not NOS) OEM stylus, it’s best to go with new here. Hard to beat an Ortofon 2M Red or Blue for the money.

Some examples with alternates we think will take on many a more expensive modern one:

Turntable: Technics SL1200II / P2 as alternate
Amplifier: Sansui AU 717 / Luxman R-1050
Speakers: ADS L 710 / Klipsch Heresy (original)

This particular combos might be tricky to keep in the OPs budget, but it would be well worth it.