My car has 6x8s and i want to change them out for 6x5s(correct me if i can't or there is a better idea). What is a good set of coaxials or components around the 150 price range. I am willing to get an amp and my HU is still stock for now (it needs an upgrade as well). Thanks in advance for the advice.
In terms of if you can do it or not, there's almost certainly a way to get it done but depending on what car you have they may make an adapter plate, or you may have to make your own. If you tell us what kind of car and if these are going in the front or back, we can point you in the right direction.
In terms of speaker brands, I like Polk in that price range but Alpine and Infinity make quality entry level speakers as well. It comes down to what sounds best to you though, so make sure you get out and listen to a few sets before you buy.
I have some CDT sets I can probably get you for that price, maybe a little more like 175. Unfortunately I would say upgrade to a new HU and amp first and then speakers. I prefer components which need an amp for them. Upgrade in stages.