Equalizer vs New receiver

I am hooking up a 5 channel 3700w amp with 4 6.5" 4-way speakers, and 2 12" dvc infinity reference, and wanting to keep my factory receiver. My question is even though I have high to low line converters would an equalizer help "normalize" the sound going to the different speakers and the woofers in the back or will a new receiver be the only thing that will help that?

What is abnormal about the sound?

Nothing yet as it is not being hooked up till Thursday, but i was told it just wasn't going to sound good until I replaced the receiver because terr was no preamp outputs from it, or something like that sorry it's been a long day. I will however have high level to low level rca converters if that matters.

Well that's just silly. Hi level signals can absolutely be used to acquire good sound. The problem with stock receivers is they have little in the way of adjustment so IF something sounds out of whack it's hard to correct. A processor like a DSP can absolutely help in these cases but it's an investment in time and money to have on put in and tuned properly so that's something you need to decide if you wanna get into or not. I can say though that if it was me and a shop told me the stereo was gonna sound bad after they install it due to hi level being used I'd be looking for a new shop to use

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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Well I've had my stuff installed for a few days now and i see what the guy meant when he said not sound right. There's noise in the lines and if i remember correctly back in college when i had my last system it also had a factory radio and the same noise was present in it. So I've decided to go with a new receiver. Now i just have to decide which lol. BTW speakers sound great! Just have to wait till the guy gets back from vacation so i can ask how he tuned everything cuz I'm not sure how high i can take the volume up without damage to the components.

There is no where near enough information to give an accurate answer to your question.
First you would need to test the signal coming from your OEM headunit to see if you have the proper signal to feed you amplifier. You will also need to know it the system is amplified from the factory. If so then this may also become an issue as some factory systems can output up to 40 volts and most high to low converters can not handle that.
Now that you know what the signal looks like we will need to see how high you can turn up the OEM radio before you send distortion to the new equipment.
Now that you have done all the testing and if you have a full range signal coming from the OEM radio you can then input that into the aftermarket amp IF the amp can accept the signal.
If all of that is good going into the amp, then there should be no reason for there to be noise as there is no place for noise to enter the system if everything was correct till this point. If the amp has a bad ground or that the point where you have connected your high level input, those are really the only way to get noise into that system.
If you were to tell us the vehicle make and model, what equipment you installed and where your connections were made and how we may be able to help diagnose the noise or at least lead you down the correct path to test.

The vehicle is a 2013 Hyundai elantra sedan without nav system. The equipment is: Boss pv3700 5 channel amp, 2xkicker cs654 6.5" in the rear door, 2xboss p65.4 6.5" 4 way speakers in front doors, 2x infinity reference 1262w 12"subs in sealed box. The way it's hooked up is with 4 gauge amp kit (recommended by boss) each door speaker is connected to a channel 1-4, and the subs are on the 5th channel which is for subs showing a 2ohm load to the amp. The amp has built in high level input converters, and for channels 1-4 high pass filters and low pass on the 5th. The sound from the speakers and subs is good except for the noise when volume is down (like a high pitched whine changing with engine speed). I haven't taken the factory volume level passed 12 and i think it goes to 40,and at 12 it tops out at 105db. To test the output of the factory system would i use a multimeter?