In-ear Headphone Advice Requested

I recently bought a pair of Audio-Technica M50 headphones, which sounded great for the price, but returned them because I didn't like the heavy, enclosed feeling of full-size, around-the-ear headphones. I now find myself wishing for in-ear headphones with sound quality similar to the Audio-Technica's. Does such a thing exist for a price that ordinary mortals can afford? I've listened to in-ear headphones that were very clear and detailed, but the music didn't have the "weight" that it had with the Audio-Technica headphones.

Suggestions appreciated.
Klipsch S4 or S4i earbuds. Excellent sound under $ 100.00
Etymotic 4. Read some of the reviews and see if they sound like something you'd be into.
I use a pair of Shure SE115s. They sound very good and are comfortable enough to wear for extended periods. They are much better in all respects if you use the squishy foam ear pieces instead of the regular plugs.
I'm thinking about upgrading to the SE315s.
I've owned a pair of Sleek Audio SA1's for several years & REALLY like the way they sound.They have a natural tone that allows hour after hour of listening pleasure & are not very expensive.What I like most about them though is that I mangled the cable a year or so ago & a replacement was readily available from SA for a nominal fee.Highly recommended!
I use the Yuin PK1 and PK2...both are excellent. PK1 needs a solid amp to really make them shine. PK2 will run off iPod amp without issues.

Thanks for the suggestions, everyone. I will look into some of them.

I already own a pair of Klipsch S4i earbuds, which are truly outstanding for the price (I paid less than $60) but pale in comparison with the full-size headphones I returned.
I'll second the Shure recommendation.I auditioned a bunch of brands all in an hour with my iPhone using the same three songs and they came out on top every time.
I've got an old pair of Sennheiser CX500 'phones that I've been very happy with. No longer made, but from what I've read the current CX300 mkII has a very similar sonic signature which is why I'm recommending them particularly in your situation. The CX500s are clear and nicely detailed but also smooth with a slight but not overdone boost in the upper bass/lower mids that adds some weight to the sound you may have been missing with the other (maybe more neutral/linear) buds you've tried. Plus they can be had for $34 online, but make sure you buy from an authorized dealer since there have been instances of counterfeit Sennheisers out there. Best of luck.
Etymotic HF5's -- about $110 on aAmazon; the 4s's if you can spring for $240. I have had both for years. They are absolutely superb. Best in-ears I have listened to in or near those price ranges. I Listen to the 4S's every day on train to work and often remark to myself how good they are.