Prices are for USA residents...
Sony MH1C - $35 from ebay. Love/hate (mostly hate) type of J-cord.
Audio-Technica ATH-CKS77 - $44 or $45 for factory reject (can get brand new boxed version for about $70 via Amazon USA as Japanese Import) version from artistic.life ebay seller. Most of the time they are just fine audibly. Sometimes they are shipped with raw drivers that need tons of burn in and/or just sound bad. In this case they will replace your pair no problem.
Audio-Technica ATH-COR150 - $20 shipped on ebay or $20 + shipping on Amazon (unless you have Prime). These are new. Keep an eye on this thread (
http://www.head-fi.org/t/586909/the-discovery-thread-new-jant71s-take-on-the-new-ath-clr100-pg-618-zero-audio-carbo-basso-pg-601) for more impressions soon though.
TDK MT300 - $25 shipped on ebay or $24 + shipping on Amazon (unless you have Prime). Here's the thread on them (
http://www.head-fi.org/t/640889/surprise-tdk-mt-300-4-97-of-awesome).
TDK EB750 - $18 shipped on ebay or $20-$21 + shipping on amazon (unless you have Prime). These are supposedly an upgrade over the TDK MT300. Here's their thread (
http://www.head-fi.org/t/651094/surprise-tdk-eb-750-6-99-of-better-awesome-w-special-guest-tdk-ie-500-ceramic-housing-to-follow).
I have personal experience with the S4 you're replacing and with the MH1C, the CKS77, and the MT300, and I can assure you that those 3 (and very likely the other 2 listed) are all a significant upgrade over the S4. They are all bass heavy as well with the CKS77 being the bassiest followed by the MH1C and then the MT300.
Happy reading!