meraklya,
As far as amps go, start with the Decware with no preamp and stay with it until your ears are used to it, then try your other amps. Rather than add a preamp to balance the channels, I would work with room acoustics to get the balance. The less you have in the signal path, the purer the sound. The Super 3XRS will reveal any upline change. Also, the Decware amp is a tube rollers dream in that you can tailor it's sound.
As far as speaker placement goes, just play around until you get the experience you are looking for. I have considerable experience with the Super 3XRS and the SE84ZS, and they synergize beautifully. The advantage of your small room is that you won't have your Decware anywhere near clipping, and so be able to enjoy all the dynamics it is capable of when not pushed too hard. Done right, nearfield listening is hard to beat.
CR