Should I get a power amp?

[Uni]

I am connecting my teac UD-505＋CG-10M clock (which i like it very much for headphone) to my Denon X3800H (running pure direct mode) to my KEF R3 for listening music.
I am wondering if I can add Topping PA7 to the chain (RCA for X3800H pre-amp, XLR for UD-505) to improve the music listening experience. Somehow I am wondering the X3800H, although running pure direct mode, is altering the tone and sound quality. I want to have to more dynamic and clarity to the result.

I have no experience of using stereo power amp so very hesitate to spend more on this just for trial and error.

Any advice is welcome.