Newbie question

roycerichards, welcome,
All of the above is good advice and food for thought.
Why buy a vintage receiver and then add a power amp while you can still get new or modern used fine integrateds or even seperates? What are your speakers that demand so much power? Start from there to see exactly what your real needs are and what do you want to achieve. 

G

The most important thing I think you should know is the relationship of power to decibels.

It takes about 10x the power to sound 2x louder.

There's little difference in maximum output between a 120 W and 150W amplifier.

Matching an amp to your speaker based on the speaker's minimum impedance is more important than a few watts of difference in rating.

Best,

Erik

C’mon guys. It’s a "newbie question. Cut him some slack. There was some good entertainment in the remarks though, it’s only funny to the initiated.

@roycerichards

There is some good info. IMO, buying vintage is only for those with the technical skills to revive it and keep it going. It was mostly good in it’s day but wore out today. Don’t get caught up in watts. I’ve had 35-350 watt amplifiers. The best were the lower wattage. It comes down to design and parts. Lower watts need higher efficiency speakers than the high power ...... 90db+. This is part of what Eric means when he said, " Matching an amp to your speaker ". Don’t know what your system consists of now or what your budget is, but an integrated amp is your best bet IMO. Hope this helps. BTW, welcome aboard.

1.  Why the need for soooo much watts?

2.  Who manufacture a 2500 watt amplifier?  Bridged?  Per side! 

3.  True.  It does not matter how much power your "vintage receiver" has.  You should not be connecting it's speaker outputs to the inputs of this monster amplifier.  Use the PreOut -  Power In loop connections.  These bypasses the power amp section of the receiver.  McIntosh has tuner preamp units.

4.  Howeeeever.  I have worked on Car Amplifiers of huge wattage that had speaker INPUTS on it.  Is this is the way you're going? Ummm, 2x's.  Now the power amplifier in this receiver is Very Important.  You will be amplifying, big time, any and all distortions coming out of the receiver.  That goes for it's front end too.  So don't vintage or cheap out totally on this receiver. 
The second ummm is,  My mother told me "If I don't have something good to write, keep my fingers shut". 

I appreciate everyone’s advice and knowledge. I should have added that I have 4 cerwin Vega mtx400 15” 3-way floor speakers rated for 400W max. I personally prefer to listen to my music at very loud volume.