What is the weak point in my system?

The streamer absolutely matters.

Agree that the streamer matters.  I upgraded from a Blusound Node N130 to an Innuos Zen MK3 and the sound difference in my DAC was noticeable.  The source is second in importance after the speakers in my experience.  

Here’s some AI feedback…
 

Deciding what to keep and what to replace in your audio system depends on multiple factors, including your budget, listening preferences, and long-term goals for your audio setup. Here’s a breakdown of your current components, their strengths, weaknesses, and recommendations for improvement:
### Current Setup
1. **Bluesound Vault 2 (Streamer)**
   - **Strengths**: Versatile, decent sound quality for streaming, easy to use.
   - **Consideration**: If you’re happy with its functionality and the sound quality meets your needs, you could keep it. However, if you want to explore higher-end options or have dedicated digital sources, consider looking into higher fidelity streamers like those from Lumin or Auralic.
2. **Chord Qutest (DAC)**
   - **Strengths**: Excellent clarity and detail retrieval, known for neutrality.
   - **Recommendation**: Keep this piece if you’re satisfied with its performance. It’s highly regarded and should work well when matched with a high-quality preamp.
3. **Rogue RP-7 V2 (Preamp)**
   - **Strengths**: Dynamic, good imaging.
   - **Weaknesses**: Midrange glare, lacks tonal balance compared to expectations.
   - **Recommendation**: Since you’re struggling with glare and tonal balance, consider replacing it. While it has some strengths, the midrange glare can be a significant issue for many listeners.
4. **Audio Research LS27 (Preamp)**
   - **Strengths**: Neutral sound, absence of glare at moderate volumes.
   - **Weaknesses**: Slight foggy sound, less dynamic compared to the Rogue.
   - **Recommendation**: Keep for now while you explore other options, particularly if the midrange glare is less problematic at moderate listening levels. Experimenting with different tubes could improve clarity and dynamics.
5. **Parasound A21+ (Amplifier)**
   - **Strengths**: High power and good overall performance; good match for Vandersteen speakers.
   - **Recommendation**: Keep this amplifier if it meets your power requirements and sonic preferences. It's a solid choice for driving your speakers.
6. **Vandersteen Treo CT (Speakers)**
   - **Strengths**: Smooth, coherent sound with good staging and image.
   - **Recommendation**: Keep these as they are known for their strengths in midrange clarity, provided you can match them well with upstream components.
### Recommendations for Changes
1. **Replace the Rogue RP-7 V2**:
   - Look into higher-quality preamps that have a reputation for dynamic sound while maintaining tonal balance. Some brands to consider include:
     - **McIntosh**: Known for smooth yet detailed sound.
     - **Modwright**: Offers a warm, engaging sound.
     - **Audio Research**: If you prefer the house sound but want something newer, check their latest models or the REF series for more dynamics and transparency.
     - **Pass Labs**: Known for their neutral and transparent sound.
2. **Evaluate the Bluesound Vault 2**:
   - If you’re looking for a sound quality upgrade, consider testing higher-end streamers (like Lumin or Auralic). If functionality and convenience take precedence, you may keep the Vault for now.
3. **Consider Tube Experimentation with LS27**:
   - Before making a decision on replacing the LS27, try different NOS tubes to see if they enhance clarity and dynamics. Brands like Telefunken or Siemens may provide the desired improvements without needing to replace the preamp entirely.
### Conclusion
In summary, keep the **Chord Qutest**, **Parasound A21+**, **Vandersteen Treo CT**, and consider replacing the **Rogue RP-7 V2** with a more neutral preamp that supports your desire for dynamics and clarity. Experiment with tube selection for the **Audio Research LS27** before making any final decisions, and assess the streamer’s performance to determine if a new model could enhance your system. As you make these changes, ensure each component works synergistically for optimal sound quality in your listening experience.

why are we taking the ideas of an LLM who doesn't listen or have the ability to listen and evaluate audio? WTF

I think that when people say there's no difference amongst streamers they're really referring to entry level gear.  If someone says their Wiim sounds as good as an Innuous Statement I'm gonna have to call BS.  I moved up from a Node with LPS to a higher end Aurender and there are distinct differences.  With a higher end streamer you will get:  Better clocking, better DAC (if applicable) more robust digital outputs like isolated USB and balanced AES, much better noise suppression.  All of this adds up to lower noise floor and less jitter.  What I found in my system is much better soundstage, and most importantly smoother sound (less unnatural dB peaks and valleys of emphasis that's not native to the recording).  

Another lane to try is switching DACs.  Different DACs truly sound different.  If you're fighting glare maybe try a ladder DAC.  Lots of guys has had great success with this and I would think it's worth a try.  Good luck and cheers.