Could use some amp suggestions

threshold amps will drive virtually anything with good quality sound especially the 400a.and forte made by threshold is a little more budget minded.

If you don't have a balanced preamp, don't waste your time/money buying a balanced amp.
I personally think 2 Adcom 5500s would be fine driving these.
If I remember correctly, some of these Kappa speakers had a difficult to drive crossover scheme, that can be modified to make them easier to drive.
Adcom 5500s can be bought here regularly for under $500.00
each. Try to find later production with IEC power cords,
then you can tweak the sound easily...

Doing a bit of Googling for the Kappa 8.1 specs I found a list which indicates a 6 ohm imp, 89db speaker system which can handle UP TO 300wpc.

I doubt very seriously you need 300wpc to adequately drive these units from what I read.

Rating a speaker at a max power handling of 300wpc isn't a remarkably high rating. As a 4 way speaker with 6 ohm nominal impedance rating, finding a good brand amp with 100 - 200 wpc into 8 ohms should prove sufficient power in real world terms.

The butler TDB 5150 will drive them. An Odyssey stratos plus will too, so will all the other amps listed here... as all of these produce real watts.

The question thereafter for yourself is not so much then "how many watts" but "which watts"?

Tough speaker if I remenber right;maybe Odyssey,Belles,Jeff
Rowland and Classe in addition to the several excellant solid state already mentioned.What is the Budget?

I would go for Class D amplification in this case if you want multichannel. You can get excellent results with those Kappas. The D amps can put out tremendous power, in a small footprint and can easily accommodate 5 channels. Wyred4Sound makes excellent amps for the money. Powerfull also. PSAudio would be another choice.

You woulddn't be doing your Infinity's or yourself any favours with an Adcom amp.Test drive a Bryston,BAT,Cary,Audio Research.

Check the archives… there’s plenty of amp reviews there from actual owners. I posted a review of a Butler multi ch amp recently. I've also put up a couple other amp reviews. Checking out mine or any other amp reviews here which are done by those people who have actually paid for them themselves seems to add something to the information being disclosed... like integrity, and honesty. Especially when you see that several months later on, they still are talking about it and it's still in their home audio system.

These might not all be similar to the ones ya see in the audio mags, and might not say all of those pro things the paid writers say, but there's little dout about them being genuine first hand self inspired articles.

Certainly an amp should be good sounding... if however, it can't control the loudspeaker, provide sufficient power to prevent clipping issues, and allow the squeaker to realize it's own potential, it matters very little if it's a great amp, as the match of amp to speaker is important on a few levels.

Loudsqueakers do have their own individual power needs. Some are easier to drive than others... for sure. one should have BOTH a quality amp and one sufficiently powered for the loudspeakers they are intended.

Also checking out the virtual systems for those speakers of your’s will show you what other folks are using to run their’s with and give you more ideas. I think sometimes, giving ideas to audiophiles is like giving matches to children. lol

If you are a true audiophile, you should know that quality of amp is more important than power. My favorite amps are Ayre, Bat, Audio Research.