Audio Research LS-15 with Plinius SA100 MKIII

I am going to buy a used amp Plinius SA100 KIII to play with ARC LS-15 (tube preamp). Do they match well? Please advice. I am a new bie.
You're fine. You should try. Alot depends on speakers and associated gear as well. So try. You'll never know otherwise.
The thing with being an audiophile in search of "superior sound",is that you have to "tinker"!...otherwise,don't expect to know anything if you don't put in the time/trial/error/etc. No one ever just gives it "one try" and achieves audio perfection either. Life don't work that way! Ok enough of the Political statements...
I've owned the LS16, tried the LS15. The 15 is good through it's "dirrect input"(or something like that). You'll also have to get good tubes, as stock is just marginal. As for the Plinius, it's going to do just fine as an audiphile grade amp, especially to start. You can try other amps, and pre's and compare to Your hearts content. There are better, others, and more expensive. but for the bucks, it's worth a try, and a good amp...clean, clear, uncolored, detailed, pretty, snappy...sure, why not?!
Good luck
You'll want to make sure the power amp has a high enough input impedance for the LS 15. I know on my LS 16 ARC recommends at least 40k minimum input impedance.