Some options worth consideration for transparent reverbs, IMO, are listed below:
* 2CAudio Aether or Breeze
* Acon Digital Verberate
* Brainworx bx_rooMS
* EastWest Quantum Leap Spaces
* Exponential Audio Nimbus or PhoenixVerb
* Fabfilter Pro-R
* Flux Ircam Verb v3 or Verb v3 Studio Session
* Overloud ReMatrix
* UVI Sparkverb
Demos should be available for most, if not all, of the reverbs listed to test on your own. Of the reverbs listed, I generally prefer the Brainworx bx_rooMS, Exponential Audio Nimbus/PhoenixVerb and Fabfilter Pro-R. However, reverbs are a personal preference. Therefore, some of the other options stated might suite your needs better.