How much do I need to spend to get a preamp that sounds better than no preamp?


Hello all.
I'm using an Audible Illusions L1 preamp and I think my system sounds better when I remove it from the signal path. Oppo BD105 directly to SMC Audio DNA1 Gold power amp. I have read that there is level of quality you need to hit before there will be an improvement in sound. I can't seem to find what that level is. Any ideas?
Thanks in advance,
Ben
honashagen
The chassis seems to be used for several pieces of equipment, including amplification, so maybe it is economical ? I like the looks of the heatsinks. @georgehifi I might be ready to try an LDR unit, so what do you think ? Enjoy ! MrD.
Clicking on the links provided, looks like really cool stuff. Well executed, sensible options, and nicely made. 

BTW- extrusions are pretty cheap. Maybe the most cost effective way to build a stiff, non-ferrous box. The designs strikes me as "smart" looking at the pics, like a guy who knows what he is doing and also knows where to source materiels.  
atmosphere, all I could find on the Baxandall was math and schematics. What good is that?
  mrdecibel
@georgehifi I might be ready to try an LDR unit, so what do you think ? Enjoy ! MrD.
By all means Flick me a PM with your email address listing your components, and I'll send you all the relative info on the Lightspeed Attenuator, even a diy circuit if you've got the electronic skills and test gear.
If all the impedance's and good, 90% of systems are,  I guarantee you'll never look at an active pre the same way again.

Cheers George