Dude, just call
Crutchfield if you're not sure, they're very helpful on the phone and every time I've ever called in the guys know their stuff.
I'm a big fan of JBL/Infinity lineup for components but I've had fairly good luck with Kicker as well. I'd suggest you buy a step up from entry level though, that's the biggest bang for your buck upgrade, from there you start to hit diminishing returns quickly trying to spend more.
Alpine, Kenwood, Pioneer are sort of the top 3 HU manufacturers. I've really liked the Sony lineup for the past 7 years or so too and I'd rank them up with the other top brands with their current offerings. JVC is pretty much Kenwood with less features or older technology so a fine budget minded option. I've run Jensen head units in the past with good results as well. Durability isn't the greatest but sound/performance/features for the money are very good. Avoid flea market brand head units at all costs. They will perform poorly and fail prematurely.
You may or may not want a sub but you can add that down the road. You may want to purchase a pannel prying tool to pop door panels, otherwise if you have scewdrivers, wire cutter/crimper, and a socket set you can typically do about anything by way of replacing OEM car audio stuff.