You need at least 5 channels. This would cover it just fine.Those speakers look fantastic. Great deal. I just purchased a DS18 amp on eBay that Is probably overkill.
DS18 H-ko2 Hooligan Monoblock 2000w Amplifier W/ Voltmeter and Clip Indicator for sale online | eBay
Find many great new & used options and get the best deals for DS18 H-ko2 Hooligan Monoblock 2000w Amplifier W/ Voltmeter and Clip Indicator at the best online prices at eBay! Free shipping for many products!
How does that converter compare to this one?
AudioControl LC2i PRO 2 Channel Line Output Converter for sale online | eBay
Find many great new & used options and get the best deals for AudioControl LC2i PRO 2 Channel Line Output Converter at the best online prices at eBay! Free shipping for many products!
AudioControl LC2i 2 Channel Line Output Converter for sale online | eBay
Find many great new & used options and get the best deals for AudioControl LC2i 2 Channel Line Output Converter at the best online prices at eBay! Free shipping for many products!
AudioControl Lc6i 6 Channel Line Output Converter for sale online | eBay
Find many great new & used options and get the best deals for AudioControl Lc6i 6 Channel Line Output Converter at the best online prices at eBay! Free shipping for many products!
Or this one
SoundQubed Q-LOC5 Active Line Out Converter 2-5 Channel w/LED Clipping Lights | eBay
The Q-LOC5 safely integrates modern high-output head units with SoundQubed amplifiers. A high to low output converter also lets you tap into a powered speaker signal to add a subwoofer to your factory system.
Never used this one but it looks well made. Need to do some research to be sure.
COSMOS AUDIO EP-LOC6 SIX-CHANNEL LINE OUTPUT CONVERTER | eBay
It has 4 channel speaker input that converts them on 6 channel outputs. 6 Channel RCA Output. 4 Channel Speaker Signal Inpu. Output Impedance: 50 Ohms.