@musicrover,
Are you familiar with the Infinity Speaker Owners Forum over at AudioKarma? If not, you might want to go there and ask the question. Lots of vintage Infinity Speaker Owners there. And the have opinions......
I currently own Infinity Qb and RS1.5. The RS1.5, with it's Watkins woofer, are a more difficult load than the Qb. I'm currently powering them with a Rega Elicit-R and I really like the combination. Sounds GREAT in my medium sized room.
Given your list, I would choose the Plinius 8100 (I previously owned an 8200) or I might investigate the Shiit combo. The Vidar is spec'd at 100 w/ch into 8 ohms and doubles to 200 w/ch into 4 ohms. Doubling is typically a good sign of an amp's ability to deal with difficult loads. Also, you would have a 15 day trial if you bought direct from Shiit (5% restocking fee).
Enjoy your Infinity's. I bet they are a great sounding speaker, especially for your music preference.....
