Current system is Adcom 555 Amp
Adcom 565 pre
Rega Apollo
Totem Arros

Will improvement be seen in a change to NAD C72/Creek 5350 SE. Thanks for the feedback
I had a 555 21 years ago. Found it a bit hard and sterile back then but it sure did drive my Acoustats. Probably same with the pre. I think many newer intrgateds will sound more musical than the Adcomn pair.
check out the jolida and prima luna separates or integrated tube amps. these would be a more musical setup than the NAD/Creek combo. i used to own a pair of arros, fantastic little speaker. easy to drive. i used a small jolida integrated in my den with excellent results.
I've heard a couple different Adcom amps, they were always a bit harsh IMO. I owned the Creek for a while, it's a very nice amp for the money. It would probably be a step up.
IMO the Creek would be the best choice of what you listed.
howabout adding more Rega gear?
Try a used sim audio I-5 integrated...good match with totem for me. Upper end integrateds can be better than lower level seperates. Portal Panache Integrated is a good deal new or used.
Add a sub, add a sub, add a sub :-)

If you have to change electronics, I'd pick the Creek of the ones you've listed.
add few bucks and get krell kav300i integrated for the radical improvement or plinius 8200.
If you don't have room treatment and want an improvement this is the ticket. Room acoustics have a huge effect on the sound quality.

Consider that the average room has peaks and dips of 15db! This is like letting a child adjust a graphic equalizer for you at random. That's what the room does to your sound.

You'll hear more of an improvement with room treatment than changing amps could ever do if you have an average room. What's an average room? Good question. Please go to the acoustics circle at audiocircle or Ethan Winers site and read. Also of course do a search here and read. This could be very interesting to you.

I apologize for not suggesting an amp. The reason I suggest trying to improve your acoustics is because alot of us who've been in the hobby didn't realize how important it was for decades. It's hard to imagine the improvement until you've heard it yourself and I get the impression you're newer to the hobby than many of us here.

Btw you came to the right place for help. There's thousands of years of experience on these forums.
I suggest pairing the Arro's with warmer sounding electronics. I agree with Rbstenho about Jolida. I use the Jolida 302b integrated with the Arro's with great results; this is a very good pairing.

You won't look back.

I had the Adcom 555 amp and it was somewhat bright and harsh to my ears. I traded for Marantz reference series amps that are definitely warmer and more musical. I would next consider Jolida or Prima Luna as an upgrade. I have recently heard the Jolida 502B at 70 w/c and it would likely pair nicely with the arros.
As a tube gear owner for 23 years, I should remind you that these products require maintanence.

As regards room tuning, Warren is absolutely right. It took me about 3 years to tune the room I'm in now (been here 16 years). One of the easiest ways to reduce harshness is too get your listening seat away from the wall behind you. My head is 2ft from the back wall and just this move made a rather large improvement in naturalness. I also have strategically placed room tunes - ceiling corners, behind speakers, side walls. These also really helped smooth out the music and make it more real and natural. I've gotten to where I can hear the room as opposed to the speakers and can make adjustments to remove, as much as possible, that "room sound".
Oh yeah, I also 2nd the vote for Plinius as a quite musical SS option.
A few years back I swapped out my Adcom 565 pre for a Creek OBH-14 DAC/Passive pre. It absolutely tranformed my system and really got me back into "listening" and, consequently, audiophilia where I started upgrading everything else (and later the Creek preamp too). In other words, the 565 was the weak link in my system at the time, bettered by a much less expensive passive pre. I think a Creek 5350 SE would absolutely transform your system for the better, to the extent of a "whow" factor. Go for it.
Thanks to everyone for the input.