It might surprise you to hear this, but based on my memory, I feel the Shure SRH1540 has a practically identical overall sound signature to the Shure SE215 Special Edition (Blue). I currently own and use the sRH1540, and I have the SE215SpE but the cable's a little bit iffy and I haven't gotten around to repairing it yet. So while I'm fairly confident in my comment since I've used both relatively regularly before, you might want to still take my following statements with a grain of salt.
The SE215SpE and SRH1540 have a similar sound signature in the sense that they both have the elevated mid-bass that's hard not to notice, the unrecessed mids that's clear yet smooth, and a noticeably blunted treble section.
Where the two products differ is in the size of the image. The SE215Spe, being an IEM, has a much smaller image and sound stage, while the SRH1540, being a full-size headphone, has significantly larger imaging and less congested positioning. That said, since you're considering IEMs, I'm assuming you're ready to accept the naturally smaller imaging qualities that come with almost all IEMs.
For $150+/-, I think the SE215SpE's a pretty good bet if you're really dead set on something that sounds very similar to the SRH1540.
Another consideration for something that sounds like the SRH1540 is the TFZ Series 5, but I've only demoed that IEM once, so can't give you any solid comparisons sound-wise beyond "I think so". For a bit less money, you get a bulkier earphone, less isolation, what I remember to be looser bass than the SE215SpE, but of course, a cheaper earphone.
Hope I've helped.