First thing I am not an audiophile, I have had the following and been more than happy with them
 
Grado SR 80's
Sennheiser 555
JVC xr700
 
I am basically in these 770's for 35 bucks.  I traded a phone I paid 90 bucks for them and 55 bucks.  I have not received them yet(did the deal on a site I buy/sell on) but can't wait to try these.  I will be using these casually, mp3 player and computer.  I didn't have an amp on my previous headphones and was fine with their performance but I was thinking about getting one of these cheap fiio or cmoy amps I have seen on ebay.
My main concern is the bass may be too much, I don't listen to rap but as of now I am using cheap ear buds so anything is an improvement. 
 
Oh does anyone happen to have a cheap cmoy or fiio for sale?

Heya,
 
The bass will be very present. They're super comfortable cans, but you may need to loosen the grip of the headband via some stretching at first (if they're new). They do benefit some amplification. Even a small amount. I found I liked them more on my portable amp when I was carrying them around. The highs/treble are good, not shrilling. The mids are recessed compared to highs/bass because of the bass. These headphones are colored to the lower frequencies. For a basshead the bass is what they're after which is where these headphones get talked about most. For someone not into a lot of bass, they will seem too bassy. A simple EQ to lower the low frequency will change the sound of the headphone quite a bit. They're a fantastic headphone too regardless. So if bass is too much, simply EQ down a tad, and keep tweaking. Also these cans have great isolation, due to pads and grip of the headband. You can get an E11 for like $65 new, less used. Some E7's used in the $60ish range. I wouldn't bother with an E5. I've seen some E7's floating in the source sale forum.
 
Very best,