Looks like I have the exact combo you are aiming for - Kef LS50, topping dx3 pro DAC/Preamp, XTC Edge A2-300 power amp.
I feed it from a RasPi using an allo signature hat & also have a minidsp HD so I can smoothly integrate a BK subwoofer.
It's beeen a long journey getting to this, having had many cheaper amps (class AB / class D), and only just got the subwoofer integrated properly with the minidsp.
The sound is absolutely spectacular now, I'm so pleased I have stopped looking at alternatives (after 2 years of twiddling). I would say that the sub is required on the little Kef's, and to make it not sound overdone / muddy, you do also need something like a minidsp HD so that you can integrate it with an active crossover.
I send everything over 80Hz to the Kefs, anything below to the sub.
Having tried a few different amps to get the Kefs to sound amazing (which I knew they could be) - my thoughts below:
Allo Volt +d (60W per channel at 4 ohms). Too anemic, not enough bass, distorted at reasonable listening volumes.
Topping PA3 (80W per channel at 4 ohms). Felt stronger, but again distortion at or around normal listening levels.
SMSL A8 (icepwer 125 based - 125W per channel at 4 ohms). Almost good - but still felt that the sound was just 'good' not incredible.
IOTAVX SA3/PA3 combo (class AB - about 180W per channel at 4 ohm). Sounded warmer than class D, but out of control boosted treble & woolly bass. Not as good as the ice125W IMHO. Very dissapointed.
XTC Edge A2-300 (icepower 300 based - 300W per channel at 4 ohms). Incredible sound, very smooth but detailed, bass was superb but clearly had reached the limit of what the LS50 could produce & pushed me to integrate the sub.
Now incredible - do not see how any system could be better in a medium size room below maybe £20k spend.
I would definiely now say that the Kef ls50 really needs a strong amp to sound at it's best. It's decent with less capable kit, but once you hear it in the sweet spot, it's a completely different animal.
There was a big difference between the ice125 & the ice300 - and it's the first time I think I have reached the capability limit of the kef. So annoyed I did not go with better kit earlier.
So yeh - XTC edge a2-300 + topping dx3 pro looks like about £700 & would be a superb combo for the ls50. If you find the bass 'not quite enough' then another £750 would get you a decent BK subwoofer + the mini DSP HD.
Not super cheap, but I reckon you would need to spend hugely more to get much better sound in a reasonably sized room.
I'm rambling now, but even on medium volumes you can have 'Oh My God' moments listening to the right tracks. That right there is all I need to stop checking reviews of new kit!
