First of all, don't buy that piece of crap.
Get something with a CD player because trust me, you'll kick yourself without it.
Card readers don't usually give out the best sound, either. Especially not walmart brand.
And at 60 watts, it won't be very loud.
I tried buying used radio's from friends for a while and none of them worked right. Finally went to Best Buy and bought a pioneer cd/mp3 player with an aux input for $75. It was well worth it.
As for the amp, just go to a car audio store, or even at walmart in their audio section, and get the wiring adapter. Plug it in, then match wires color to color and you're good to go.
Well, Crutchfield advertises DUAL, so it can't be all that bad. Flash drives/cards can give sound as good, if not better than a CD. Think about it.
CD: digital info on the disc, converted to analog audio signal.
Flash media: digital info in memory, converted to analog audio signal.
However, the flash media has the advantange of being scratch proof, it can be updated with new music at any time, and isn't limited to 700mb. With a CD you'd have to burn a new disc everytime you get new music, it's easily scratched, and limited to 700mb.
Now power output, the OP is (i'm guessing) still running the stock speakers. The stock speakers are 15watts max, so that 60watt x 4ch stereo will be a perfect match to the speakers. It'll be loud enough. Any more power than that will blow the stock speakers anyway.
I've got a Pioneer mp3 cd/usb player too. I've had it for about 4 months and I've use the cd player maybe once. I've just been using my 2gb usb flash drive, and can't detect any difference in audio quality. Oh, and I've got Pioneer TS-D601P 260w 6.5" speakers up front, and TS-D901P 350w 6x9" speakers in back. This is my 2nd aftermarket stereo with cd player in this car, and the 1st with usb. IMHO, the flash media is far superior to the cd. Hell, most aftermarket stereos have ipod support. Guess what ipods are flash media. Have you even seen anyone walking around with a cd player lately? Nope, just ipods or some other mp3 player.
Bottom line is the sound quality depends on the encoding. 128kbps vs. 192kbps vs 320kbps. The higher the kbps the better the sound. I have my audio files at 192kbps or 320kbps.