I'm with Al, goose, and 91idi.
It's really up to personal preference/budget.
Don't need to be able to win some sound comps, but be able to hear over that diesel rattle and road noise.
Those headliners are pretty sweet, plus the kick panels.
Now for a story. A friend of a use to be friend got everything bought for him by grandpa. (TransAm ws6, 04 chevy z71 put lift and big tires. You name it, grampy bought it for him.)
Well on the 04 chevy he (grandpa) spent almost $2k or a complete new system: deck, speakers, amps, subs, etc.
I put the EXACT same setup in my brothers 02 z71 and it sounded way better. Night and day difference. I think the only thing different was speaker/sub/amp brand. My brother paid less than ¼ the price.
Also most shops will try to talk you into new speaker wires, NOT needed IMO.
I tend to prefer Kenwood, Alpine, and Sony for decks.
Kicker, Sony, Alpine, Kenwood, and JVC are all pretty good speakers. The Sony's will be cheaper and sound just as good.
On decks, I prefer one's with built in ipod control, HD radio, and personally I still use CD's also. Also look for one with a dimmer function.
Those one's with changeable display color are pretty nifty.
For subs I mainly stick to Kenwood and Alpine. There are way better one's, but overpriced IMO.
I don't have any real preference for amps. Just make sure it'll handle the load, has the features you want, and ALL the adjustments.
Do NOT buy the cheapo Walmart amp installation kits. Talk about shiat. You'll get all kinds of interference, and they like burning out the fuse holder.
My all time favorite deck was a Dual. It was silver with a red display. Didn't have all the features, but was excellent for radio and cd use. Clear crisp sound.
Oh another thing to look for. Antenna booster. I have some old one from a yard sale, I pick up all "local" stations crisp and clear with it. Not mandatory, but nice to have.
Last but not least, install it yourself. Oh and maybe look into some sound deadener.