The Krell k-300i “only” puts put 150Wpc into 8 Ohms but doubles to 300Wpc into 4 Ohms. I don’t know what speakers you might be planning on buying in the future, but I’d think this would more than adequately power just about anything.
But, if you must go nuclear the Plinius Hiato puts out 300Wpc into 8 Ohms and 450 into 4 Ohms. Best of luck.