Most powerful and popular EL34 tube amp?

Check out the Raysonic SP 100.If you don't mind the Shanling like styling,Some of the original(not Mk. II)models may still be available at discounted prices.I purchased the KT-88 version(SP 120) and it will drive all but the most difficult speakers!

Depends on SPL (in db's) you wish to obtain at the listening position. Both 89db speakers and 4ohms are do-able, assuming the 4ohm is their lowest impedance droop and you are driving the speakers a lease breaking levels. Do you have budget limitations? What kind of speakers are you going to drive?

My max budget is $1500 (for used).
It will drive Tyler LSS (one piece). (Is it 89 or 90db?)

I already have VK-200 and VK-30, but want to also keep a tube amp which would work better than VK-200 for different styles of music. BAT VK-60 may be an ideal choice, but I have some EL34 tubes (by Siemens) and want to use them. Also, VK-60 is a bit more than my budget. That's why.

Canary CA 160.

I have a pair of your speakers in my closet. They are 92db and I had no problem driving them as loud as I needed in a 19.5x13.5x9 ft room with 40 wts.

The best sound I got out of these speakers using an amp with EL34's (SED Brand) was a Primaluna 1, a simple integrated unit which I'm sure sounds nothing like your BAT's. Probably warmer and less transparent/resolved. I found I liked the LSS's sound best, especially thru the mids and highs, using amps with 6550's or KT88's. In my room these speakers had a less than perfectly linear tone thru the mid/upper mid range and tubes with too much color (emphasis) at certain frequencies could sound a bit edgy. Maybe it was my room or ancillaries.

Power wise I tried 5 different tube amps from 40 to 160 wts and all had sufficient power to drive these speakers off 4 ohm taps, and in one case 2ohm taps, so finding an amp with power is not so much an issue I think as is getting one with proper tonality.

Sorry I couldn't be more specific or help. If I had to make a WAG I would suggest, in that price range, you consider a VTL or Manley amp using EL34's - they have a good reputation and a fairly modern sound (for tubes).