Do you guys really think it would be a step up to take the pioneer out and replace it with a good preamp?
It depends on what you're looking for. If your goal is to add more realism and depth to the picture, a tube preamp will help, but it probably won't be dramatic. If you're looking for a big change, I recommend replacing your amp and preamp with a tube integrated. To my ears, tube amps make everything sound more natural -- especially vocals and stringed instruments. 50 tube watts should be plenty if you play at moderate levels. Jolida JD302b and Cayin A-50 T should be in your price range.
If you play at high volumes and you're looking for more punch and dynamics, I recommend a more powerful amp. Your Sonance is underpowered for that. Stereophile measured your Stratus Gold at 84 dB efficient. They need more power to really rock.