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You may want to hang on to the large advents. These are still viable even today.

I'd look toward the frontend of the system first....those Advents may surprise you with modern equipment.

email me directly and I will give you a number of a guy in N NJ that can take a look at the amp for $50 or less so you can tell how good of shape the unit is in.

Replace the Kenwood. After 20 years, I got back my original piece of "hi-fi" equipment, a 626 Pioneer receiver. Put it into my system and took it right back out. That sweet sound of youth can be improved upon. At least half the fun of hi-fi for me is snooping around to obtain used equipment to upgrade my system.
Just make sure what you get truly is better than what you got.
Good luck.

I have some Original Advents that I refoamed. I hooked them up to an Arcam A65 plus and it sounded great. Repair the Kenwood and sell it. The Thorens is worth keeping if you can tune it up. Good luck!

I would sell the Kenwood "As Is". It is not worth the time and effort to get it fixed up. The old solid state sound is bad-bad-bad. I know, I have an old Marantz receiver that was pretty much state of the art around that time and I now find it unlistenable.
The Advent's can sound very very good, I also have a pair of them. They look very dated and are just plain unattractive; I wouldn't have them in my living room.
The Thorens TD-160 is a fine turntable and if it has a good quality arm I would get it tuned-up. Depending on what the tuner wants to tune it up. The problem is that if the tonearm is not a good quality one then it would be a waste of money to tune -up the turntable. If it doesn't have a quality arm and you op to put one on then the cost to tune it up plus the cost of a good arm would make it money poorly spent. You can get a relatively new Rega planar 3 for $350-400. That is cheaper than the cost of a tune-up and a good arm. In addition to that, one of the best values in arms is already on the planar 3.
So the table is the only piece that I would advise you consider updating. If the caveats mentioned above are taken into consideration. There is so much out there that is newer that has such great value and has a much higher performance level. If you have about $1,000 to spend, you can put together an excellent system that will be reliable and will sound and look fantastic. Don't underestimate the appearance factor. I didn't spend all the time and money I have spent to decorate my living room to then casually throw in some old ugly audio gear and ruin the overall appearance of the room. Much of the older stuff,especially electronics, will need extensive repair work to make it reliable. Even after the repair, most of the old solid state stuff will still sound bad.
I would recommend the Nad C320BEE integrated and NAD phono pre-amp both used for a toal of around $400. The Rega planar 3 $400. There is a pair of Acoustic Energy Aegis 3 floorstanding speakers on sale hear on Audigon for $250. Put this system together for about $1,075 including shipping and you would have system that would look and sound very very good. And no, I am not selling any of this equipment. I have heard it all and I am recommending it to you because you would then have an updated system that I feel you would love.

Good recommendations but the Advents only cost about $20 to refoam and if the screens are clean you can get someone to refinish the wood. I think it could make nice furniture.