I can offer three suggestions to consider that are not the usual candidates. All three can stay powered up all the time:
- SMc Audio VRE-1C - This is one of the most natural solid state preamps out there. Unfortunately, it is above your price range and almost never comes up for sale used. However, you can still have most of the magic with either one of SMc Audio's new stripped down versions, or by having them modify an old McCormack TLC-1 preamp (like mine). These are active preamps with typically +6dB gain, (although mine is a unity gain version) and they provide all the bass and rich tonality you would ever want. Contact Patrick at SMc Audio.
- Life-Changer Audio icOn 5 - These are passive AVC units using Dave Slagle's autoformers in copper or silver. They sound very natural with very good bass, great tone, and just a touch of warmth. Srajan at 6moons uses one in his main system. I owned the 4Pro balanced unit and it sounded very good driving my amps with input impedance of only 10K ohms. The icOn 5 uses a switchable input buffer to allow the full performance to take place with partnering equipment of any impedance.
- Hattor Audio Ultimate Preamp - A very good sounding solid state preamp, and amazing for the price. Get the dual mono, with AMRG resistors, and passive/active switchable gain (0, +3, +6, or +9 dB) using the op-amps of your choice (Staccato, OPA2134. Great display, remote, and outboard power supply. Other manufacturers use their volume controls.