You will only benefit from an upgrade, no matter which brand or type of amp or preamp, with careful matching. Which means you know your system well and can realistically predict how an upgrade is likely to sound in your system. Then you can buy the new (to you) item(s) with relative confidence. But, often, this is not possible, especially when making the magnitude of change you are contemplating in combination with not having experience with ARC. Hence the value of a trusted dealer. So an audition is needed.
Recent ARC gear is very reliable and biasing is a breeze. A Ref 250 set is likely to sound fantastic and will have sufficient power. But, again, it will require an in-person audition or “audition through purchase.”
My Ref75 SE is my forever amp. But I’m running a Linn Klimax DSM/3 direct in and I’m driving Thiel speakers so my experience does not help you. But I can tell you that the current gear is well-designed and very reliable.