ep 630 's are essentially the same as the sennheiser cx300.
I don't consider myself an audiophile by any means, but I use earphones daily and have gone through many of them. I should also mention that I appreciate bass.
I've owned the koss spark plugs, sony 31's, 51's, 71's and 81's (all of which died within 6 months), JVC marshmallows, creative ep 630, sennheiser cx300, shure e2c, vmoda bass freq, Ultimate ears superfi 5 eb and more that I can't remember off the top of my head.
In the under $50 category my personal favorite were the vmoda bass freqs - but again, this is coming from someone who appreciates bass. I felt that the ep 630s/cx300 had good mids and highs, but coupled with an iPod, I just did not feel there was enough bass response.