Most IEM's, like the Shures you mention, are going to have a good bit of sound isolation. I was going to recommend Future Sonics Atrios. They have great sub bass (best sub bass in the market), which I think helps a lot of poorer classic rock recordings that are bass light.
There are 2 versions. The Atrio M5 with mg7 driver. They can be found for approx $150. Then there is the Atrio X. They are about $80 on JR.com. The main difference between the two is there treble response. The M5 has a little brighter treble but neither are considered bright. Their treble is fairly laid back. You can get the x model with an iPhone mike and iPod controls for that $80 price.
If you don't want any isolation then stay away from IEM's and go with earbuds that fit similar to the stock ibuds. There are a couple of good earbud comparison threads worth checking out.
Check out the Spider Realvoice, they won't be super isolating due to their design. If you liked the Shure's you could also look at the SE215 but they really do isolate. True non isolating sound you could look at one of the Yuin buds or if you can find a pair on sale Bose IE2 (these fit comfortably and definitely let in sound and while not great are a step up from stock buds, just get them on sale as they are not really worth heir retail), or look at a Sennheiser sporg bud or their CX/MX9xx line of buds.