OP,
First of all… it is a completely reasonable question to ask. I learned 40 or 50 years ago that there is no end to how much better a system can sound… ok… to well over a million dollars. If you carefully choose what you purchase, double the cost and you will simply be amazed at how much better it sounds and how much more enjoyable your system is… over and over and over again. So, good question.
Doing a quick review of your system… it would be easy to suggest a turntable. But this is 2022 and I find it increasingly hard to recommend that route… you have to buy disks… they cost money, take up space… if this is a major part of your interest, playing with disks… great… TT and Phonostage.
But at this point in time you can do streaming at the same sound quality for roughly the same price… and it has a future and your music library is nearly infinite… with almost no cost (Qobuz… $14.99 / month). So if you are investing… you will quickly far exceed the sound quality of your current turntable by investing in your digital end.
I recommend digital. Now what is concerning is that you are not hearing a big difference in iPhone and TT… there is something very wrong. You should.
By the way, I have worked at streaming for fifteen years… iPhones, iPads, MAC, PCs (lots of different software), and finally dedicated streamers. Currently I own a flagship Aurender W20SE streamer and it is a bargain at $22K.
I would look to getting a good streamer and DAC. For a good DAC I recommend a Schiit Yggdrasil… this fits into your component cost scheme and will perform like a unit of twice the cost ( I own a Schiit Gungnir and had a Yggdrasil for a while). This gives you a solid DAC. Then you need a streamer. I don’t recommend going cheap on it if you are trying to build a solid g system. I would recommend an Aurender N100… used if required to keep the cost down. Don’t let the folks without experience make you think your going to get audiophile performance out of a MacBook or PC. Maybe as an interim step you can use a Bluesound streamer… but you are going to get a lot more out of a solid high end audio streamer (pretend it is the turntable if this was analog).
I don’t recommend spending any more on vinyl or CDs. Go straight for high end streaming. Then next step, we can talk about your preamp… that would be next… then speakers if you want to keep going. My systems are shown under my user ID.
