If you want better isolation, the V-Moda Vibes are out. Too bad ... they sound really good and are an easy transition for a Sony user. They don't isolate like IEMs do ... they're like an equivalent to open headphones.
You can't do much better for isolation than you can with the Etymotics ER6i's. They are very different from the Sony's, physically and sonically, and might take some getting used to ... but, as the familiar line about IEMs goes, you'll hear things you didn't know were in your music. The list price is over your limit, but I got a pair online for about $89. To repeat myself, I wouldn't get on an airplane without them. However, just my preference, but I don't use them as everyday earphones ... I don't always need/want isolation (around home, for example, or at the office).
For simple canal phones that are an upgrade over the Sony's, a possibility would be the Sennheisers, or do what I did and get the Creative EP630's -- less than I paid for the Sony's, but I like them more. But they wouldn't isolate much differently from the Sony's. Some Sony users graduate to the Shure E2's, but they're bulkier and they receive mixed reviews ... but they are a possible jump for you, as they do isolate.
A lot could depend on what player you use, what you listen to, and what file size the songs are.
[Edit: Excuse me for forgetting ... welcome to Head-Fi -- sorry about your wallet.]