3 - 3.5m is a large listening distance. If you have a look at the recommendations of Genelec or ME Geithain you will see that only the biggest models are able to provide enough direct sound. Since you have a living room and not a studio the lower number of the recommended listening distance is more correct. The KH310 is a near field to mid field monitor even the KH410 is only a bigger mid field monitor (about 2m listening distance).Will this speaker work fine using it from 3 - 3.5 meters? Speakers 2.5 meters apart.
Will connecting it to Denon 3700 preouts won't be an issue?
If you don't follow these recommendations, the ratio of direct sound to reflected sound will be on the reflected sound side. The sound will be less exact and more blurry with any speaker with a wider beam.
I know you have to make some compromises but the lack of enough direct sound is a very important part. A decent speaker which provides the right beam sounds much better than a speaker which is to small but excellent.