$1,500 phono upgrade worth it?

One of the reasons it is better to run just one dedicated line and not multiple like some recommend.

Depends on the level of hum. If when playing music at whatever level and sitting wherever you usually sit the hum is audible only when the music isn't playing, ie gets drowned out by groove noise, then no worries. Mine has been like that a lot of the time, and I can tell you when the music starts you just won't care! 

But if the hum is there and you can hear it even over the groove noise between tracks then it is probably worth a little effort. 

First make sure the turntable, phono stage, preamp and amp- the whole system really- is all plugged into the same outlet. Not the same exact outlet obviously but all from the same wall outlet, conditioner, power strip or whatever. Anything at all plugged into another AC source connected to your system provides another path to ground and this is where ground loop hum comes from.

One of the main sources anyway. Could also be your turntable or phono stage are stacked right on top of something and picking up hum from that. The phono stage has the most gain of any component by far. 40 to 60 dB or more. Orders of magnitude more gain than anything else. Extremely susceptible to noise. All kinds of little things that would be nothing to a DAC with 3V output can be a nightmare for a cartridge with .3mV output. You see the orders of magnitude there?

Some guys it really bugs them and they will put in whatever it takes to get these things dead quiet. To improve a level of noise already lower than your typical record groove. So it will sound better when not making music. For the same time and effort they could have been doing things to make the thing sound better when playing music.

So make your judgments, and pick your battles.

You're new to this, unable to tell the difference between hiss and hum, and think records are supposed to sound like digital. Sorry. Whole point is they don't sound like digital.

Along with totally superior sound quality comes a pretty obvious tradeoff in terms of easy to hear noise. Yes if you are willing to move way up the line in performance and cost you can probably find a lot less noisy phono stage. This however is a lousy way to do it. Because you will never, ever get it dead silent like digital.

Even if somehow you do, groove noise. So what is the point?

Focus on the music. Upgrade to a better phono stage for the music. The rest will take care of itself. Or if you prefer, embrace the suck. Whatever. Just don't try and put legs on a snake.