Upside: Up-to-the-second features, upgrade flexibility, enhanced music playback. 
Downside: Difficult to set up and configure, pricey.

An A/V pre-pro is a pre-amplifier and processor housed in a single package. It performs near-identical functions of a receiver except in two major areas: Audio amplification and radio playback. These are not supported onboard and an external power amplifier is mandatory to complete the kit, though a radio tuner deck is optional.

The segregation of these functions theoretically minimizes interference between electronic circuits which can be a challenge for the jam-packed receiver. The extra room also enables quiet passive cooling and leeway for better internal layout. An example includes PC-like swappable cards for future expansion capability.

Here you can easily upgrade to a beefier amp for more reserve power, but the tradeoff is the additional cost in wiring up the two decks. Putting aside the quality and varying prices of these interconnects, the amount required is directly associated with the number of audio channels. The more channels you plan to run, the higher the cost.

Upside: Honest power ratings, great sound quality, wide selection available. 
Downside: Fairly huge and hogs too much shelf space, pricey.

Power amplifiers can be broadly categorized into three groups: Mono block, stereo and multichannel. Each performs one, two and more channels of audio amplifications. To ensure ample reserve power, most feature one or more high-quality toroidal transformers and oversized capacitors. The former are rare in lower-end receivers due to the space crunch for accommodating all the required electronics.

To facilitate ease of operation such as automated powering up and shutting down, electric trigger are normally found on the rear. This allows a connected pre-pro or receiver to remotely control the amplifier without manual intervention via a miniplug interconnect.

Another new class of amplifiers have surfaced in recent years. These digital or class "D" models run cooler than their analog counterparts, thanks to their higher power efficiency. Form factor-wise, they can be up to a third the size of the usual offerings.