Budget Tube Amp (newbie)

I owned Large Advents for 20+ years and used them with a variety of SS and tube amps. My experience is this:

1)  If you've never upgraded the crossovers, this is the place to start. There are way better components available now than when HK designed those speakers, and it's drop dead easy to do the upgrade. You'll be amazed at the difference.

2) Large Advents need at least 30W/ch if you play them at any volume above background. So while I love and own Decware, only the Torii Jr and above will work, and that's out of your budget.

3) The ST70 or its variants is a perfectly good choice, but you'll need a preamp. As the CR1020 has preamp outs, it would work fine. My first tube amp was an ST70, and I used the preamp section of my NAD 7140 to drive it. You can move up to a dedicated preamp if you like the direction you're heading.

4) If I was in your position today, I'd get the Rogue Cronus in a hot minute. It's a quality unit and will enable you to get a taste of tubes at a very low cost and if you don't like it, you can resell it at very little loss.

Have fun with this! I eventually sold my Advents for more than I paid for them, and that was after 20+ years of enjoyment. Good luck on your journey!

Thanks, for the advice armstrod! I really appreciate it!
 Best regards,
Rob

Don't overthink it. Look for something that you can sell for about what you pay. Don't consider anything glittery and new that will drop in value overnight. Regardless of what you hear on these forums, sound quality has not had the quantum jump that some would lead you to believe.
When I had Big advents, many years ago, my Marantz 8B had way more power than necessary. That's a 35 watt a side EL34 unit that's a collectible legend of relatively undistinguished sonics. I've had a couple of those and Model 5's. Great look but way overvalued.

Honestly, my Dynaco ST-35 was a fine match for those speakers. You can find a modestly priced 20wpc unit of some strip pretty easily used. Those that have suggested a mid-priced tube integrated are giving you good advice. Don't jump into the deep end of decreasing returns. A good integrated should give you the essence of what you're looking for.

There’s some good advice already here so I’ll just add this. The comment about good transformers is key, and old iron can’t be beat. Go vintage, but get something with the power supply caps redone unless you can do it yourself. That’s easy with point to point wiring in vintage equipment. Use vintage tubes.
Don’t spend a lot. Start with an integrated to see if you like “the tube sound”. One of the best you could do here is a Scott 299C. It was my introduction to tubes and changed the way I heard music. I had a $$$ surround rig and after hearing the 299C it was game on.. But beware, tube amplifier collecting is addictive. 
Move on to a good tube preamp and power amp. Here I like some of the newer preamps, but stay with vintage power. I have plenty of both but my favs are my Wright 6SN7 based preamp and Quad II power amps. The Wright has open architecture that makes for easy tube rolling, which you will become addicted to. KT66 power amps like the Quad II’s are a good choice, smooth and neutral. A lot of the Dynaco power amps that have been modded also fit the bill. 
Going tube is a journey, deeper than the solid state road. Enjoy.

Hogwash!
Old iron is no better than new iron. A good design is a good design.
A great 60W KT-88 amp is a Citation II, but they are pricy.
Lots of old vintage stuff is in need of a complete rebuild, not just capacitors.
Tube rolling is silly. Get something that sounds well and be done with it.

Just enjoy the music!