I think either MX560 or MX660 would be worth your money. Here is an article you might be interested:
headphone:
Sennheiser MX560 earbuds offer good comfort and improved sound quality versus "stock-issue" buds provided free with iPods, laptop computers, PDAs, or Mp3 player devices. Proprietary Sennheiser 'BassWind' design delivers a bit more punchy sound in the bottom-end versus Senn's older MX-model earbuds or the junker earbuds given away with mobile players. These earbuds are basically identical to the current Sennheiser MX660 model but without a volume slider control built into the cord, so they're a hair slightly better-sounding versus the MX660 due to the lack of an added resistor in the line. However, some may feel the convenience of the volume slider worth the tiny hit in sound quality given the non-audiophile application.
Black cosmetics with a nifty flash of chrome makes the MX560s stylish but not overly conspicuous-looking earbuds. Soft mesh comfort pads help with getting an appropiate earbud fit in the outer ear. The package includes a cord winder for easy cable length adjustment and a soft travel/storage pouch. The approximately 3.5ft cable terminates to a right-angled gold-plated 3.5mm (1/8") mini-plug. A 2-year Sennheiser manufacturer's warranty is standard.
SENNHEISER MX560 black 3.5 mm Gold-Plate Connector Earbud headphone with Basswind $29.99
HEISER MX660 black 3.5 mm Gold-Plate Connector Earbud headphone with Basswind $24.99
With the similar price, you might also consider MX760, Here is another article for you to decide which one to choose. Personally, I would recommend this one
For your reference:
headphone:
Good price for quality 'on-the-go' Sennheiser MX-760 earbuds. The short earpiece cable length is ideal for use with high-end PDAs & mobile phones/Mp3 player devices. The handy extra extension cord included with 760 allows extra cable slack if wanted and the provided cable winder accessory is perfect for tangle-free moves while out & about. The accessory also assures neat cord compatibility with any remote control access your player device or cell phone might offer. Decent sonics too given their affordable price with a mild emphasis on a clean non-muddy bass response.
The MX-760 come in an attractive flash-grey on black color scheme. A quality 1-meter extension cord with a gold-plated right-angled termination is provided standard for those listeners desiring a bit more overall cord slack. Two mesh-foam earpad inserts provide some small degree of MX-760 fit 'adjustability' although, like any earbuds, the quality of the in-ear fit can be hit & miss for many listeners, thus impacting the sonics. Handy earbud travel/carry pouch included. The strong 2-year Sennheiser product warranty on the MX-760 remains a nice plus.
SENNHEISER MX760 black 3.5 mm Gold-Plate Connector Earbud headphone with Basswind $29.99
Hope these can be helpful.