Alright so I'm looking to upgrade the speakers in my car. I'm not a speaker guy to any degree at all. I do not know anything really about them. I just want a decent/good sounding system that won't break the bank. I'm really not looking to spend more than 500-600 bucks if possible. Don't care about name brands either. If you know cheap speakers that sound good I'll take them lol. I also don't really need subs for the rear compartments, but some low range would be nice. I dunno, help me out

Any suggestions will be very appreciated.
Here's what needs to be filled:
Speakers
- Dash - None
- Doors - 5 1/4" woofers, 3/4" tweeters
- Rear Side Panels - 3 1/2"
- Rear Stowage Compartment - two 5 1/4" subs
Alternate sizes/locations
- Doors will accept most 6 1/2" speakers
- Rear Side Panels will accept up to a 4" speaker