If you love the sit3 and find that it has enough power, you may consider buying a second and running them as single channel monoblocks. I believe you will find that the sound is significantly improved by allowing each channel to have it's own dedicated power supply. I did this for my (diy) first Watt F4s and it made a huge difference.
All you would need to do to perform this mod is to pop the top and desolder the power supply connections for the channel you won't be using (and put wire nuts on the ps cables so they can't contact anything conductive). It's easy for any tech to perform and simple to reverse if you want to change back at a later date. Impossible to screw up, really.
I'll note that you can get a taste for this impact without the modification simply by running only one channel of each unit and inserting a shorting plug into the input of the unused channel. Unfortunately I've found that even having the unused channel pulling power while idling impacts the performance of the side you're using.
The best amps from all designers use a dual mono topology for a reason...
