Hi,
I heard the 604 mk3 in a showroom, that was larger than your room. It had rotel gear running it. It imaged very well, however, it sounded a bit foward, diffenetly not warm sounding. I have not heard a recent B&W that was warm, I think they tend to be analytical. After only two weeks, you might continue to tweek how the system is set up. I noticed you mentioned hardwoods...I assume hardwood floors. If so, you might want to put a big thick rug down to absorb some of that floor reflection, that may make the sound a bit warmer. 2 feet from rear wall sounds about right, but it sounds like you have some room with the side walls; having walls that are either 12 or 18 feet wide and the speakers that like being around 7 ft apart. You might change the wall you have the speakers set up on. Also, if the speakers are around 7 ft apart, I take it that you are between 7 to 9 feet from each speaker? (or that is where I would start sitting to find the sweet spot.) In addition, if there are windows, glass doors, etc. these things can really mess up your imaging and give you a bright sound. Drapes can help. In addition, if there a TV between the speakers, that soemtimes can mess things up- if you do have a TV between the speakers, I would pull the speakers out a foot or two in front of the TV. 12 X 18 is not that small of a room- I wish you luck. I run a pair of Spendor 3/5 in one of my bedrooms that is 10x12 and it sounds very nice. However, while the Spendors are rich and image very well, they are not the best for rock and metal.