LS50 + Amp Power

@b_limo :  the signal chain is kind of complicated as i'm trying to optimize for several inputs and outputs:

Use: 
HT/Gaming: 50%
Vinyl: 45%
Digital: 5%

Input: 
TT: Fully KAB modded technics 1200
Phono:  Parks' Puffin
DAC:  ToneBoard
Gaming box / streamer / etc. = HDMI digital sources.  

TT and Dac are sent to an A/B splitter to route RCA to:
+ Bottlehead Crack Headphone Amp
+ VSX1120k

Digital sources for gaming are sent directly to the Pioneer.

Front 3 channels are LS50s w/ a PSA 15" Sub.

I'd love to have a separate setup for vinyl & dac, but I don't have the room or budget.  Ideally, I'd like to use the 1120k as a preamp of sorts and use preamp/out to run into a separate power amp for the LS50s.  Only need 3 channels (or really only 2 technically for L/R). 

Not sure what my other alternatives might be, that's why I was headed in the direction of separates.     

I have ls50s running off a $80 Fosi bluetooth Class D integrated amp bought via Amazon, about 40w/ch, size of a pack of cigarettes. Sound surprisingly good! VEry good even I would say! I was a little shocked when I heard.

They ran very well off a pair of $6000 list price 500w/ch Bel Canto ref1000m monoblocks prior. I have newer ls50 MEtas there now. Was going to sell the original ls50s but they work so well in their new place off a modern amp that cost so little I decided to keep them.

So you just never know. I would not choose to use most affordable tube amps with ls50s. Have yet to hear them sound good that way.

No matter what, you should add a sub capable of filling in below 60 hz or so to as far down to 20 hz as possible always with ls50s for complete results. They are small and cannot deliver muscle in the low bass no matter what. Use white noise (available to stream off internet) and a sound meter app on a smartphone to blend the sub in well. Need not be anything fancy to do that...tools available to most for little or even nothing these days.

The OP might do well to checkout the new LS50 Wireless IIs and matching sub.  $2500 plus sub -- don't know cost of sub -- could eliminate concern about matching electronics and speakers.  Darko's review suggests KEF has done it well.  It makes a neat looking setup that's ready for streaming and Roon.  I'm going to try it for our living room.

Re crossovers:  I was pleased with the result of raising a pair of Velodyne HGS-15s that supplement KEF Reference 1s from 40 to 80 Hz.  I'd recommend OP try 80 Hz with the LS50s.

New KEF subwoofer technology recently announced:

KEF's KC62 Subwoofer Packs 1,000 Watts Into A Tiny Cube | Digital Trends

I told a dealer to order me the KC62 yesterday whenever that is possible. I am thinking of using the wireless connectivity kit from KEF for this.

So Krell K-300i + LS50 + KC62 sub (maybe wireless)

"KW1 Wireless Subwoofer Adapter Kit | kef" https://us.kef.com/kw1-wireless-subwoofer-kit.htm