Worth Upgrading Marantz 1504 AV Receiver with Power Amp?

i haven't heard your avr, tho it appears to be fairly modestly powered. although some mainstream avrs like nad have better amp sections than others, i personally haven't heard a mainstream avr which didn't benefit from external amping, and the named parasound would likely be a significant upgrade.

not sure re SQ of chromecast

but get the Parasound from one of the many dealers that allow free returns and do a listening test

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Here's some current listings here on AG. Any one of them will be a huge upgrade from what you now have. Some of them are a little over budget, but you may be able to negotiate for a lower price.

Yes, adding a power amp to your AVR will be a huge improvement and one that you will immediately hear.  The Parasound A23 will be a very good choice.

But do you need an AVR at all?  If you only listen to 2 channels, then I suggest getting rid of it altogether and buying a good 2 channel integrated amp with a built-in DAC instead.  Pick the right one and you won't need an external power amp either.  This way you'll still get a better power amp section and the benefit of a superior preamp section as well.

Do not underestimate the importance of a good stereo preamp.  The preamp sections in AVR's, even in "pure direct" mode, are a mere afterthought.

mb1audio - thanks for the listings. A lot of older power amps but I don't think Class A/AB has advanced much in the 21st Century. 

Paraneer - I thought of an integrated amp, but I need the bass management that the AVR provides because I have the speakers too close to the wall so high passing them and using a small sub helps quite a bit. The Halo Integrated would be perfect, but I'm a bit frugal. ;-) 

" mb1audio - thanks for the listings. A lot of older power amps but I don't think Class A/AB has advanced much in the 21st Century. "

I'm not sure I Get your post because you're asking for A/B amps. I've heard all of those amps, and owned some of them. They sound nothing like each other, or an A23. For example, most people would take a McCormack DNA-125 for $900 over any receiver on the market and the A23. Technology is one thing, haveing the skills to implement it is something else entirely. Nelson Pass, CJ and YBA are made by companies that help define what state of the art is. 

That said, my recommendations were made in error. I didn't realize that you intended to keep the AVR as a preamp long term. I assumed you would be looking to upgrade to a preamp similar quality. It still makes sense to upgrade the amp because more power usually is usually a smart move. But without a matching preamp, you'll never hear what the amp can really do. A much better fit for your goals and equipment would be something like Emotiva. You'll get the extra power that you need, but you won't be wasting money on more expensive products that your system won't be able to take advantage of.