My current faves are built into the Eden ENX/WTX260 and Genz Benz Streamliner 600/900 heads.
Both preamps are smooth, clean, quiet, and warmer than average (the Genz more so than the Eden). The Streamliner also provides a useful tube overdrive function, via a full 3-tube preamp.
Both have excellent "audio swiss army knife" capabilities in terms of aux inputs, pre-post DI, headphone outs, etc. The Eden has particularly powerful EQ, and starts out flat with the controls at noon. The Genz has a definite pre-shape at noon, and doesn't have quite as broad an EQ range. However, the Streamliner's EQ is perhaps the most musical I've ever used, in that even extreme knob settings are still useable.
Both are rackable. Interestingly, both are smaller and lighter than most rack preamps, yet they are full-service heads, and include a handy buit-in class D power stage. This makes them even more versatile. My Genz is the 900 watt version, and has MUCH more punch than the Eden, which is really only big enough to handle acoustic sets, jazz trios, rehearsals, etc.
The Eden is also available in pedal format, as a preamp/DI only. Note: if you are looking at the Eden heads, the WTX is preferable to the ENX, which doesn't allow you to defeat the onboard compressor. IMO, the Eden's compressor is by far the weakest element of the whole design.
