Hi @michaellent:
I agree with @tomic601 and @solypsa that a tonearm with only 8.5g effective mass may not bring out the best sound that a Kleos is capable of. No doubt that the combination will track well, but possibly with reduced energy in the lower octaves and lessened dynamic impact.
The Lyras will work OK in tonearms of 10~12g eff. mass (for example SME Type V, Technics SL-1200G), but will sound progressively better as the effective mass increases. Normally I'd suggest 16~18g as the sweet spot, but they also sound exceptionally good in super-rigid, heavyweight arms like the SATs and Kuzma 4-Points (including the SAFIR-9).
As suggested by @tomic601 , you could add weight to the headshell, but that is an added complication which you may prefer to avoid (given that this will be your first foray into MC cartridges).
Regarding an SUT, the 5.4Ω coil impedance of the Kleos should not give any difficulties to most SUTs.
However (and this applies to low-medium output MC cartridges in general, not only the Lyras), most MM-gain phono stages incorporate capacitance at their inputs, which is necessary for equalizing the signal from high-inductance cartridges (MM / MI / IM), but is neither needed nor particularly desirable for an SUT. An SUT performs better with very little capacitance between its output and the input of the phono stage, whether due to a interconnect cable which is excessively long and/or has more capacitance than it needs to, or capacitance which is part of the loading scheme for MM / MI cartridges.
In closing I recommend first searching for an MC cartridge that is known to sound good in the Pro-ject RPM tonearm, next work out how much gain needs to be added by a stepup device to make your Aric Audio Special phono preamp happy, and then decide if you would like to use a transformer or headamp for said step-up device.
hope this helps, jonathan carr (Kleos designer)
PS. Can more manufacturers of MM-gain phono stages offer defeatable input capacitance, for use with SUTs??? 😉