How important is the amp?

If you like what you hear and can hear differences when you tweak then I can't think of a good reason to change.

Wait, oh yeah, because there is always something better!!! of course! You never know for sure sometimes unless you try.

If you are content, you will just enjoy listening to the music. If you are not, don't loose sleep. Look for something better now! Money and time is all you have to loose.

Seriously, only you know if you are happy with what you have, but in your case, it sounds like the vital signs are good.

No amp, no sound.

Good amp up to the task of driving speakers to their max, great sound.

Then there is everything else in between.

So it's pretty important I would say.

The room used and its acoustic properties is perhaps the single biggest part of a home system and the one you have least control over to change as needed. So after that, you have to have speakers that can perform well as needed in the room. Then you need an amp up to the task of driving the speakers to their potential. Now you have a solid foundation for good sound you can tweak as needed. After that, you are in a position to focus on teh quality of the source devices used, but these days, with modern digital in particular, getting good results there is less problematic and much harder to go wrong altogether. Of course, teh quality of source material played can vary widely as well, even if all the rest is done to perfection. You have little control over recordings as well other than to try various releases and remasters if needed.