Cayin A 300B

T_ramey,
I never tried to bypass it because I don't have a decent preamplifier. My Kingko always worked as integrated. 
But according to King Ip, you will get better results if you use a good preamplifier; the preamp section of the KA-101 is not as good as the best preamps out there.
Regarding tube rolling, replacing the preamp section tubes (the small 12AU7 and 12AX7) will increase a bit of the sound quality, but the real improvement comes from the rectifier tube. Originally the amplifier comes with a chinese 5AR4 that is decent, but not spectacular. Once you replace this tube with a better one, it's an amazing improvement!
At his shop we tried many combinations and the one that really shines for me (and I was lucky enough to get a rare tube from King Ip) is the Westinghouse 5U4GB/5AS4A. Everything goes bigger, fuller, richer! Clarity, bass, soundstage... 
There is someone on another thread (maybe another forum, can't remember, but I'll search for it) that found another rectifier tube to be fantastic for the KA-101. Different flavours, so many possibilities...
Anyway, I advise you to contact King Ip regarding any question. His English is not perfect, but he's an amazing guy, always willing to share his expertise and knowledge. He will answer all your questions.

Awesome, thanks for the reply migueca!

You're welcome. 
By the way, I found the comment from the user toro3, here in Audiogon, regarding tube rolling.

Looking at his KA-101 I saw a different rectifier tube. When I asked about it, this was his answer:
"...that’s the smooth black plate RCA 5U4G with round mica at top and lower d getter. I prefer the 5U4G over 5AR4 and 5U4GB due to sounding richer IMO".

This user, toro3, has a system similar to mine: Kingko amplifier and Omega speakers. You can find his system and comments here at "Virtual Systems".

Any idea if it can take a 274b? I have a couple of those as well as several 5u4 types. My speakers are very efficient Klipsch so the low wattage from the Kingko is appealing. 

I asked King Ip about that. His answer is Yes, you can use those tubes (274B and 5U4).