1. The Dynaco Stereo 70 Power Amplifier - They're relatively cheap (between $300 for a rough one in need of a refurbishment to $850 for a complete "frame off" from the ground up rebuild) easy to maintain, reliable, and there are A LOT of Stereo 70's in the world, making them easy to come by. Fact: an in spec, properly maintained Dyna Stereo 70 sounds more than sonically respectable. If you haven't heard one you're missing a sonic benchmark that you need in your experience-set to be able to tell whether a five or six-figure tube amplifier is all it's cracked up to be.
2. A Scott, Fisher, Pilot, or Dyna FM Multiplex stereo tube tuner - Personal aesthetics aside, it really doesn't matter what brand you have as long as the tuner is from that golden age; post FM Stereo but pre transistors. Models including The Fisher FM-100B, H H Scott 350D, and Dyna FM-3 sound wonderful when they're brought back to original factory (or kit) specifications. Tether them to a good antenna and FM or Free Music is yours. If you have a decent FM station left in your town you owe it to yourself to enjoy it through a tube tuner.
3. Quad ESL 57 Speakers - ESL 57's, more so than even Quad's newer models, tell you everything you need about state-of-the-art midrange reproduction. But because the midrange is so right-on we try to match it in the bass and the treble with subwoofers and super-tweeters. Bad idea. Or should I say, "noble cause and a valiant effort," that some of the best audio minds of a generation couldn't solve. But it taught everyone what a discontinuity between drivers sounds like. Still, a pair of Quad ESL-57's driven by a Marantz 8B in triode mode in a mid-sized room can sound as close to "real" as any mega-buck system...
4. The Original AR XA Turntable - The AR XA turntable is a tweaker's dream. Acoustic Research sold a boatload of 'em and you can find replacement and upgrade parts for nearly every part in the unit. You can, if you wish, spend a lot of money upgrading and refurbishing an AR XA, but there's always a point of diminishing returns on mods. With fully tricked-out XA the best you can expect is the same approximate performance level as a mid-90's Linn LP-12. That's nothing to sneer at, but a used mid 90-s LP-12 sells for only slightly more than a fully modified AR XA.
5. Dynaco PAS-3 Preamplifier - The ultimate workingman's tube preamp that you could build yourself on your kitchen table in a couple of nights after work. And if you didn't have too many beers while you were assembling your PAS-3, when you turned it on the darn thing might actually work! I've seen some kit-built PAS-3s that had real problems because someone who was instruction-phobic built them. I've also owned a kit-built PAS-3 that was far nicer than anything that came from the factory in terms of precise wiring, clean soldering and overall attention to detail during assembly. Like the AR XA turntable, you can modify the heck out of a PAS-3. Frank Van Alstine has been doing mods and making kits based on his PAS-3 mods for many years. Like the other gear on this list, if you haven't heard a PAS-3 I its prime how can you know how good a VTL, or Lamm, or Audio Research preamp really is? The Pas-3 is the tube preamp base-level performance and sound benchmark.