Newbie question

A receiver is a tuner, pre-amp and amp built into one chassis.

An integrated amp is a pre-amp and amp built into one chassis.

If you are going to buy a vintage receiver and want to add an amp to it, essentially bypassing the built-in amp, you will need to buy a receiver that has L&R line-level pre-outs. Many receivers do have this feature, however many inexpensive units, i.e. low-power units, did not have this feature.

High quality vintage receivers are cool. I've owned a couple. However, they are old and may require refurbishment and/or repairs to get them into proper working order. Additionally, they often require periodic cleaning of the volume/balance/tone controls, etc. They also will not have remote control.

Unless you really enjoy the nostalgia of a vintage receiver, I wouldn't recommend one, just to use it as a pre-amp/tuner. And unless you listen to over-the-air radio, I wouldn't recommend a receiver at all.

There are lots of really good integrated amps on the new and used market. I would get the best quality integrated amp I could afford and not have the need to add an external power amp and hopefully it would also have remote control.

That's one man's opinion and YMMV. Good luck in your search.

2500 watts???!!!!

Keep reading....

It appears you're caught up in the "I need more watts" mindset.

2500 watts isn't nearly enough. My wife's hair dryer has 3000 and she's always complaining it's not enough. One sure way to know you have enough watts is when you turn the amp on the breaker blows. Preferably the main breaker. When you have to add a whole new 200A panel just to serve your amp then you know, ...it is time to add another amp. When you get to 2500 kW then we can talk.

Yeah, 2,500 watts with the right speakers will make your ears bleed and you’ll be half-deaf in no time. That said, @reubent is 100% correct. An out of date receiver is not the best way to go. If you are trying to add to power your current receiver, you can only add more power to one if it has the pre-outs as stated above.  If you are worried about not enough power, I’d suggest you start with an inexpensive pre-amp and buy an amp with say 200-300 watts, if you find you really want/need then you can swamp it out for a bigger amp. Or even bi-amp. If you like really like retro looking (I do)  buy some used Mcintosh stuff.