why a high end phono preamp?


I recently purchased a Hegel 160 integrated amp with no phono stage.  I also purchased a NAD c 427 tuner, and have a Dual CS 5000 TT (I have no idea what type of stylus it uses).

I wish to play my vinyl's but don't understand why I can't do with a $49 phono amp as opposed to one that costs hundreds of dollars. 

Is it the Hegel that is responsible for delivering superior sound, or is it the preamp? I thought the cheaper item is solely a conduit for the power, but is it the product that allows the record to be heard properly? Any recommendations for my components? I was looking at Clearaudio Nano V2. Thank you.
pharmacylaw
I'm sure someone more technical can explain this better but a phono preamp is taking a very small signal and magnifying it many times and also applying a riaa equalization to the signal. No small feat and how well it is done is definitely going to affect sound quality.

You don't have to spend a fortune for an outboard phono stage, the new Parks Puffin punches well above its weight at $400. My $1000 phone stage is for sale now after getting the Puffin.
+1 jbhiller " A quality phono preamp makes a huge difference"
IME, this is absolutely true. I've used preamps that were stated to have excellent phono sections (melos & Jeff Rowland) & didn't get the sound quality I was looking for until I went with a dedicated phono preamp. The first one was a sonic frontiers signature phono amp. The second is Audio Alchemy's latest with optional power supply. Big difference.
"Is it the Hegel that is responsible for delivering superior sound, or is it the preamp?"   Everything, from the quality of your vinyls, to your speakers/room acoustics, is responsible for superior sound.   A chain is only as strong as it's weakest link.  
With the best amps and speakers, you can't make up for a loss upstream. A good phono section is mandatory for good vinyl playback!
For a budget of $500-$600, I’d recommend either the Lehman Original Black Cube or the ifi unit mentioned above. If you’re on an even tighter budget, you can try the Schiit Mani but you should splurge for a linear power supply if you go that route. A good/decent phono preamp does make a difference but it should be within reason given the turntable/cartridge sitting behind it. I think your planned budget is within reason.