If you think your current Topping is a bit "clinical" you might want to try one of the Schiit headphone amps. I have an Asgard and a Lyr 3 and think both are excellent sounding. The current version of the Lyr can be run without a tube. Schiit also just released the Kara preamp which includes a headphone amp. No tubes and it has been getting excellent reviews.