Cartridge break in

Unfortunately going up the hifi ladder can be difficult as one upgrade will bring out the next weakness in your system.

The Lyra Kleos is not a bright cartridge, it is very smooth and transparent. Perhaps a little hifi sounding compared to a dynavector and perhaps the SS.
Your musical surroundings phono now has to use an additional gain stage for the mc signal. The ms phono is now your weakness as it can sound mechanical and lean.

You replace the ms phono with something better and the Kleos will start singing.

Tuff decision, as IMO if you want to get the most out of the Kleos you need a better phono stage.

I'm unfamiliar with the Musical Surroundings SuperNova, but in principle I concur with Downunder. An inadequate phono stage can distort the richly detailed but very low level signals produced by really good LOMCs.

There's reasonable debate over the "best" order for upgrading turntable vs. tonearm vs. phono stage. IME, upgrading any of these yields positive results.

OTOH, there's almost no debate (among those with experience) that ALL THREE must be up to snuff before undertaking a major cartridge upgrade.

Disproportionate cartridge upgrades are often disappointing, either because a high end cartridge reveals weaknesses in its support system (TT and arm) or because the phono stage can't cope with the depth of detail.

From my own components... my $8K LOMC sings like a goddess on my main rig and phono stage. She does all the audiophile things but in a coordinated way that makes ravishing, lifelike music. However, she can sound miserable on an entry level rig or feeding a low quality phono. If I'd bought this cartridge before having a suitable TT, arm and phono I might not have been happy.

OTOH, I've tried several inexpensive MMs in my main system and most play way above themselves. A $275 MM can fool people into thinking that it's a $1-2K cartridge.

TT, tonearm and phono stage first. Cartridge upgrades should wait.

DU and DD,
That was my first thought; that the new cartridge had exposed some limitation in the system.
I'll let the Kleos break-in before looking at the most obvious possible sources: the phono stage and/or the preamp.
The Musical Surroundings has been well received in the press and has been a pleasure to use. It has two great assets: it is dead quiet (possibly because it is battery powered) and it has three independently adjustable inputs. I have an old Thorens that I use exclusively to play 78s.
Any suggestions that would work well in the Aries/Kleos combo?

Manley Steelhead: I finally broke down, traded some gear that was idle, and got one and it is so much more refined and detailed than any other I've owned before. Large chunk o' change but the Kleos will definitely thank you for it. Also, Parasounf JC3 or Aesthetix Rhea are candidates from personal experience. Not in the same league as the SH though.