Your only problem is your amp section is unable to handle 4 ohm loads which is VERY common. Onkyo/Integra are known for being 4 ohm unstable as is Yamaha etc. Dennon and HK should be ok and most of the big amp seprates of course can handle this with ease, thats what you pay for
Arcam make very nice and highly regarded gear, and I did check for you, it is 4 ohm capable for sure.
The Integra is NOT 4 ohm capable and your sales person either doesn't know what he is talkng about(very common) or lied(very common). this is from the spec sheet on the Integra website..show it to the company and Demand that they fix your situation.
90 watts minimum continuous power per channel, 8 ohm loads, 2 channels driven from 20 Hz to 20 kHz, with a maximum total harmonic distortion of 0.08%
105/110 watts minimum continuous power per channel, 8 ohm loads, 2 channels driven at 1 kHz, with a maximum total harmonic distortion of 0.7/0.9%
110 watts minimum continuous power per channel, 6 ohm loads, 2 channels driven at 1 kHz with a maximum total harmonic distortion of 0.1%
Note: it says nothing about 4 ohm loads and therefore is not capable, its that simple.
Goodluck!