I don't think either will be 100% up to the task. I've read here that people on the Polk forums do not recommend running the LSis with the 3805. With just 3 of them though, you should be able to get away with it. You can always add an amp down the road if it seems like they need more power. My speakers are all 4 Ohm too, and my Marantz didn't like driving them, so I added the monoblocks.
Sony doesn't make great receivers, IMO. Even the ES line just doesn't sound that great to me, though I have to say I haven't heard the most recent top-teir models. To be completely honest, when someone says "audiophile", Denon isn't at the top of my list either. The 480x and 580x do sound nice, but that's getting pretty pricey and I'd probably opt for separates at that price point.
I know you mentioned you had a NAD before, I'd recommend looking into a 763 or 773, also Rotel, Arcam, B&K.