This is a GREAT "Biggest Bang for the buck" list.simple solution, learn how to do it yourself, we're here to guide you, this is not rocket science lol. lots of tutorials on how to take out a head unit for your vehicle model on youtube. Save that installation money and get everything you need. Another vote for the clarion head unit mylows10 suggested. buy it from sonicelectronix and request for a dash kit, should be waaay less then 110 for a 2010 accord, its not a bmw where you need all the bells and whistles. Also pioneer speakers 80 and under sound like sh*t best buy, frys, and other unknowledgeable stores always seem to recommend them but... THEY EFFING ****, unless you get the upper/top tier components, i would not touch a pioneer speaker. You dont need rear speakers or if you really cant live without it, buy em later, the front speakers are the most important and should get the most attention.
here's a simple bang for buck buy list
head unit : Clarion CZ702 In-Dash CD/MP3 Car Stereo w/ Bluetooth & USB Port make sure to contact them about the dash kit
speakers : Image Dynamics CTX-6.5cs (CTX 65 CS) 6.5" CTX Component Speakers or
JBL P660C 6-1/2" 2-way Power Series Component Speakers System
speaker/subwoofer amp: Precision Power PPI P900.5 (p9005) 5-Channel Phantom Car Amplifier and a sub from parts express website (get a 15 if you want to save money and get a little bit louder.)
use the rest of the money for wires, amp kits, I dont think you'll even need the big 3 upgrade running this little power, use that money on a good sub enclosure, treating and deadening your doors, make a good baffle and seal.(just cutting a wooden circle to mount the speaker and putting weatherstrip tape covering the edges). This should result in a really nice sounding and decently loud system.
Installations vary a lot in price, and some shops just don't install products purchased elsewhere. doing some things yourself can make a big difference in what you end up with (In some cities it takes close to $700 to $900 to just cover a good install)
You might not have enough cash to do everything, so you might have to prioritize. Know that you won't get loud without a sub, and your speakers won't sound great without deadening your doors.