I'm not sure a 1:15 would be that much of a problem -- the XLPS-V3 appears to have plenty of overload margin -- provided your preamp is comfortable with the level presented it may work
A more problematic issue may be load matching from cartridge to the step up -- the MK10T has a listed input impedance of 18ohms and the Delos an impedance of 8.2 ohms. Lyra state "recommended load via step up transformer is 5-15 ohms" so the MK10T may work -- there's a lot more discussion on this topic here
http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html
A more problematic issue may be load matching from cartridge to the step up -- the MK10T has a listed input impedance of 18ohms and the Delos an impedance of 8.2 ohms. Lyra state "recommended load via step up transformer is 5-15 ohms" so the MK10T may work -- there's a lot more discussion on this topic here
http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html