Best Amp For Infinity Kappa 8.1 Speakers

Would the Parasound HCA-3500 power amp work well with the Infinity Kappa 8.1's?

The Parasound might be a bit harsh, espescially with Kappas. Adcom's GFA555 would be a better match. Don't get too concerned about the number of watts. I only have 100 watts powering my Kappa 8's but it takes 3 boxes weighing in at nearly 150 lbs.

The Aragon 8008 is a good hefty choice for solid state at a decent price. A strong tube amp has less of an iron-fisted grip on the bass, which the Kappas respond well to, but a good one will be expensive. These are very demanding speakers but can deliver awesome results with the right electronics.

The Parasound would be a decent choice for if you want to vertically biamp. You can use different brands of amps if you use a good quality attenuator on the louder. Pots sounded bloated.

what would anyone recommend to use for Kappa 9 speakers

mfb33

Used pair of Parasound Halo JC1 in high class-A mode for sweetness, if you can afford them.
Or as daltonlanny said a Parasound HCA-3500, but it will be a touch hard.
Any Krell power amp will do EG KSA 150 200 or 250.
  
None of the other amps mentioned so far will come close to driving either the 8.1 or the 9’s as good as what the JC1’s could do.
In fact the impedance/-phase angle load is so hard on these Infinity’s that the other amps mentioned here would be doing it tough into them.

Cheers George