Audio Research or Conrad Johnson Tube Pre-Amp???


I am looking at the purchase of an Audio Research SP-9 or SP-14 or Conrad Johnson PV-9a, PV-10, PV-11 or PV-12 pre-amplifier. It's very difficult since I've not been able to hear every one of these pre-amps. However, I do want a tube pre-amp to mate with my Threshold S/300 and Mirage
OM-9 speakers. Later I plan to purchase Magnapan 1.6 speakers. I will also be using an Elite Rock Turntable with Excalibur tone arm. I will also be using two professional tape decks for recording and playback.

I really need assistance regarding the following:

1. Which pre-amp will work well.
2. I also need to know which tubes are the best for a particular pre-amp?
3. how long do tubes last normally with 2 hours daily use?

Any other information you can offer would be greatly appreciated. Thanks so much all.
4. Does turning on and off the tube pre-amp hurt it?
rbwinterlink
I would pick the Conrad Johnson PV-9a over the two ARC only because I like the CJ sound and better power supplies than in the sp-9 and 14. My opinion only, sure some will disagree?
I have owned or sold every model that you list. I like the older CJ sound, but like the ARC better. IMHO, the ARC gear is built much better than this vintage of CJ gear. I almost always had trouble with dirty volume and balance pots, bad turn-on relays and noisy switches with the CJ. Never a problem with the ARC.

The CJ sound tends to the warmer, darker, sweeter side of life and the ARC has better bass control and throws a wider and deeper soundstage.

If you decide on the ARC, make sure you get a SP9MKII or MKIII. The SP14 is wonderful. I think the phono stages are superb in either one. Plus, these only require 1, (SP14) or 2,(SP9)of the same tubes. Makes tube rolling easy and inexpensive. The CJs have many more tubes of different kinds to replace.
I owned the S300/series Threshold and tried the Audio Research Sp 9 mk1 and mk2 ..Hated both..Way to bright and shrill...If you going to go to Audio Research to match with the Threshold you might consider the older sp8 or sp6 ..Also as mentioned the C/J would be a good choice..Another very nice piece which will mate very well with the Threshold is the Classe 5 preamp..Very Sweet Solid State pre but sound gorgeous with the Threshold..The Classe has the sound of tubes without the hassle..Also built to last....
To get the best sound out of the Conrad or ARC make sure that the input impedance of the S/300 is at least 10x or 100x greater than the output impedance of the preamplifer. That is why Thorman thought that the ARC was bright and shrill and why the Classe sounded very sweet.

If build quality makes a difference the ARC is better.