Conrad Johnson CAV 50


Just acquired this beauty from my father in law. I've never owned a tube amp, so not sure if I should sell it, or keep it and pay him. Anyway, a question for you tube heads. One of the EL34 tubes in slot V7 ( a tube which can have it's bias adjusted, which I assume means the power transmitted) has it's red light constantly on. I turned the bias all the way down and it still flickers. However, I noticed that my left speaker sounded blown/distorted. When I turned the bias up, the distortion decreased. The instructions say to turn the bias down/counter clockwise, until the red light goes out. But, if I do this, it sounds bad. So, my question is this. Is it simply a tube I need to replace to fix that problem, and if I change one tube, should I change them all. Next question is I searched for the EL34 tubes and of course there are a large variety of them. Any thoughts. To me the amp sounds little bright with the Celstion SL6's I am using, so any warmer tubes would be nice. Also, if I were to sell this setup, any idea on what I might ask on pricing? Thanks.
Roly
rolyasm
So I am getting my record player back today. Should sound great. I am in need of a pre amp for it and wondering if I should go with a Tube Phono preamp and how that might interact with my CJ. Looks like they start around $180, whereas some of the SS ones go for $50. I would really like to keep it around $200, but willing to go more if the opinions are that it will make a  big difference. 
Also, BradwBradley, I see the sensitivity of the Kef LS50 is 85. Is that going to work well with my amp that doesn't put out a ton of power? 
Hi all, just bumping this. Been playing with the amp and different speakers and having a fun, interesting time experimenting. Just ordered some vinyl that isn't scratched, like most of my collection, but still need a pre- amp or some way to connect the record player as there isn't a phono input. Any suggestions? 

Been researching a bit and this one looks promising for a reasonable price. Puffin Phono DSP. $399 . The  ART DJPRE II Phono Preamp Audio Interface gets good reviews for a $50 product, but it sounds like a lot are using it on basic equipment that just doesn't have a phono on it.