receiver preouts help

I would suggest, borrow an amp from a friend or dealer.
There is lots to be gained---that is if you are familiar enough to the sound you are now getting to be able to hear the difference gained.
There are a lot of second hand amps in that price range;that will better what that receiver gives you.
AND,yes it is a simple disconnect/connect(some receivers have bars/straps that you remove---some don't.---Read your manual.

Emotiva carries 3 and 5 channel amps new in the $600-800 range. I agree, bi-amping would take a load off.

Your speakers have biwiring terminals if I'm not mistaken, so you could bi-amp to get more power to any of them. To get it right you'd want an amp that has the same power and tonal characteristics as your Pioneer--ideally a power amp from them that had trim controls so you could match the gain between the inboard amp amd the outboard. Marantz made a five channel amp (MM9000?) that sometimes shows up here for about $500 and that could work since it has input trim controls, but i can't say if it would be a good tonal match.

You can do this for any number of channels. Some prefer to add a big quality power amp for the front three speakers only but that is your choice. I cannot recommend any amps in that price range and wonder why you are asking. This AVR is good for more than 100WPC, all channels driven, and a 200wpc will get you only 3dB more power output.

Kal