[BLK03GXS]

In the past i have helped manny freinds that end up with systems that dont do what they want based on a h/u that isnt up to par.. that being said you dont need to spend big money to get one that will do what you want.
Unless you want to run componants, or have to complete with high spl (lots of bass) i would steer you away from amping your speakers w a 4channel esp if you aren't verry experanced and want to install yourself.
Being an Alpine fan i have had doz of their h/u`s amps and speakers/subs over the years and am still a fan, so personally that would be my choice for you in this case. Pick a H/u with high power output, some of the alpine decks even requite a standalone amp type power connection due to the rms power that they make.. This power makes for good clean sound out of coaxial`s.
For the front 6.5`s are a bit of a fitting but not super difficult for a newb. i have had Lots of luck with the S series alpines in 6.5 or even 5.25`s which are easyer to fit..
allso infinity, jbl, or JL`s allso sound great.
as for the rear i believe currently i have JL 6x9`s.
take the extra time to run the wires that usually come with your new speakers from the deck(unless this has already been done) and bypass the stock harness.
For most ppl that aren't into making your licence plate shake this sounds great, and if you want more... its easy to add a single 10 or 12 that will take less then 1/5th of your trunk space. and has been my exp that even with 2 12`s or even 2 15`s my front stage was able to keep up... but anyway. Just mho.

Oh and if you yank your deck there's a good chance that who ever installed it may have not spent the 4-15 bucks for the gm antenna adapter.. could b why you aren't getting radio..