Help power pair of Infinity Kappa 9's please

You may want to look at some of the professional gear for the Kappas.
Pro amps run 2ohm loads all day long for years, I don't think the Kappas are going to provide a problem.
You may be suprised at the sound quality of some of the better amps on the market, and they should be within your budget.

May be a viable option with some research.

When you are talking about those kind of low ohms, I can't help but think of car audio.
The lower the impedence, the more power you can put into it.
I am sure they are designed to take the power.
I would seriously look at the pro stuff if I was in this situation.
Since they are designed as such, I am sure they could take the power of a pro amp, or they would not have been designed with that impedence in the first place.
They want power, give em power!
The only reason consumer speakers are designed with an 8ohm impedence is to play nice with the 88 billion receivers & sub par amps on the market.
If they wanted to put some power into their speakers, they would not be 8 ohms.
Do some research.
Apogee, Crown, Creston, and some of the Mackie amps sound good, and would not have a problem with your Kappas.
You might just find Nirvana (literally) with the right pro amp.

When I mentioned car audio, I was really thinking about the low impendences (which are similar to car audio), and did not even think of using car amps, but now that you mention it..........
The kapppas would sound great with a Phoenix gold 450 or Zapco running them for sure.
I have alot of respect for the musicallity of some of the car amps.
I own some premium 12volt products myself.
There are some truely excellent car amps on the market, as refined as any home amps.
As far as sound quality goes, I would give the advantage to DC current!
I would worry about the electrical conversion though.
Ac to Dc.
May introduce some noise and negative effects.
Not really sure.