but I know eventually there would be times when I wish I had more headroom when I ether have a low recording, feel like jamming out super loud, or upgrade to speakers that could be more demanding (like Dynaudios).
This, combined with the @jeffbij comment makes your decision for you, bridged amps at high volumes and demanding speakers will melt down. I would stick with the Sim sound that you know that you like, but consider going with a higher quality two channel amp vs the mono blocks.