Hi good morning bro.

Are you using OEM headunit or aftermarket? Because your speaker produce the sound based on HU output. So even if you upgrade the speaker but the output is the same from HU, then you might not find much difference.

But if you not into high end SQ setup, perhaps you can try  entry level Focal Auditor component and JVC KD-R971BT single din and and it will be less than 1k.. For further details, you can pm me bro.. cheerz

Audison Voce AVK6 is an high end speakers bro so you must have better amp to power those speakers.. and also high end head unit to get the best of it.. perhaps you can buy amp 1st then change the headunit later on.
high end amp within 1k a bit hard to find bro.. can get entry level focal auditor and alpine line for that price range.. but you can check with other sifu sifu here..

My 2 cent advise bro, you can do one by one if dont have enough budget bro.. ICE is a never ending journey.. 

Change ur car player and see... mo point upgrading ur speakers and ur Head unit is original..

if u want to listen everything high-end, surely it's gonna cost u a bomb.. unless you're willing to do step by step..

Player with higher voltage output should give you some heads up and of course do read up about the headunits before buying it