When you say the marantz has a garbage preamp vs a stereo integrated, what are you basing that off of?
It’s an AVR, which means it’s a jack of all trades master of none design built to hit a desired price point that’ll be digestible to the general public. So corners need to be cut, and unfortunately parts that are most important to achieving better sound (like power supplies, capacitors, resistors, etc.) are costly and thus primed for cost cutting. Add to this that in an AVR the delicate stereo signal is embedded in a very electronically noisy environment with all the digital processing and other things going on and you can begin to see why an AVR not conducive to good 2-channel performance. And, to be honest, for the general public that’s probably not a big deal because to them it’ll still sound “good” because they have no idea of what good really is because they’ve only ever heard crap.
But I said specifically in my prior post “If 2-channel audio is important to you” because if it is and you’re truly looking for “better” sound the AVR can’t be in the signal path in any way for the reasons stated above. Your options then come down to your priorities.
If you’re huge into HT and want to max out that area then yeah, a $3000+ prepro will be in the equation. (BTW, notice how fast price goes up when you put higher quality parts in the multichannel signal path vs. the price of an AVR that also includes amplification, which gives you an idea of just how much they cut important corners to achieve their selling price). But if you find the amps and surround processing of the AVR to meet your needs for HT, then why not let it handle that and just replace the critical 2-channel pieces?
That’s why I suggested just adding a stereo integrated amp. If the rest of the AVR duties are “fine,” then the integrated is the most cost-effective way to bring your critical 2-channel performance to another level entirely. And in case you’re wondering, yes you will hear a very big and significant improvement — we’re not talking minor benefits here. I, and many others here, have implemented precisely this kind of setup when we didn’t have a dedicated listening room and stereo and HT systems had to coexist, and it works fantastically well. And yes, before you ask, using a good stereo integrated will likely outperform a $3500 prepro hooked to a multichannel amp and be much cheaper as a bonus.
Ok, I’m done preaching and hopefully you get the idea. Best of luck in whatever direction you decide to go.