You can do this one of two ways.
Buy a new receiver with all the latest bells & whistles that have the preouts. Then when you are ready to add a separate amplifier you can by attaching via rca's the amp to the receiver & the speakers to the amp.
Or you can buy a separate preamp, AND separate amplification in 2,3,5,7 channels. Separates usually cost more than receivers.
The receiver & amp probably will cost less money than separates. But if you get separates, you won't be wasting money on the amp that you aren't using in the receiver.
Good bang for the buck separates to start out with are Emotiva & Outlaw Audio. They aren't cheap, but they aren't as expensive as other retailers.
Or you could get your components used from Audiogon. Good companies for gear are Rotel, Parasound, Nad, Adcom, Sunfire. Since audio products are designed to last for years, you will get good bang for the buck used & possibly jump in at a higher starting point for gear.