I heard about hybrid tube amps which is a combination of MOSFET circuitry and tube preamp. It offers a hefty 100 watts per channel(2) and tube preamp composed of mostly EL34.
I have not heard of EL-34's used in a pre-amp section as they are output tubes (pentodes, but can be wired as triodes).
There has been a resurgence in the area of integrated amplifiers in the last few years, with hybrids being the most intriguing portion. They normally use either 6DJ8's or 12AX7 (or deviations of them) in the pre-amp stage and SS devices in the outputs. I have been looking at one for a small system in my bedroom.
Some power amps use SS inputs (usually J-Fet's) and tubes on the outputs. Hovland is one such company using this method.
In the 2-channel portion of my system I am currently using a pure tube pre-amp (extremely modified Counterpoint SA-1) with a solid-state amp (modified Bedini 50/50DE) driving modified B&W 330i's augmented by a REL Strata II sub. One thing most people can not get over with this configuration is how chameleon like it can be, with album after album sounding different from one another, and sometimes song to song on the same album (Eric Clapton’s SLOWHAND is a great example of this). Cornelius, have you noticed the same thing on your system?
Most people do not believe that there are tubes in my system. I usually have to open my pre-amp and show the 5 glowing bottles inside.