This.
@gaby95 If you are going to spend the money on an Amp, you want it to make a difference. There is another thread happening where a guy wants to run his Speakers at 105dB PLUS headroom. (This is a stupid idea, and I am not recommending it for you.) I bring it up, however because in the conversation it is brought up about how much power an amp should be able to deliver to your Speakers.
The 590s are rated up to 250w. They are 6ohm nominal, and if rated truthfully, can likewise still drop to 4ohms.
My goal would be to Power the Mains specifically with something capable of delivering 300W at 4ohms. Not because you will NEED it. But because it safely covers what your Speakers may demand in a worst case scenario.
Mind... your ears will likely tap out well before that point.
This is the nature of Headroom.
The difference between 150w and 300w is 3dB. Enough to make a difference in SPL, yes. Yet anything less than that isn't really giving you anything you do not already have. except perhaps a little more juice down low when the dynamics demand a little more.
The other channels usually aren't as demanding. Center can be. But you have a different Speaker there which I am less familiar with.
Amp conversations like this come down to a value proposition... what that means to you, only you can determine. However, if you want to buy an Amp, look for the one that is going to make a difference, and do so in a reasonable budget.
There are Amps out there which can give you more juice still, but the cost starts to rise significantly. Moreover, you don't really benefit from that.
But an Amp that can give you 200w into 8 ohms, 300 into 4 would be your sweet spot using the 590s.
Again, you will likely never come close to tapping that power reserve.