Actually, I'd like some comments from you...
- Would you like a USB miner or are you happy with standalone RasPi controlled unit?
- Do you feel modular design is important, or would you prefer a nice tidy box?
- What about form factor: free or rack?
- What dB level are you comfortable with?
- Internal custom PSU or ATX?
- USB? why not
- Modular is the way to go
- Free or rack (bitbonanza style ?) depends on final price (cheaper is better)
- Low Db but i have some noctua, so not a big deal

- Well if you can provide a custom psu that lower the final price : i take ! If not => ATX
Edit : custom PSU maybe because your next rig is a Monster ? ^^