The only thing to keep in mind with soundstage is that generally speaking, the IEMs with wide soundstage are also usually open or semi-open (which means they have poor isolation). That generally means others around you can hear your music and you can hear external sounds leaking in as well. Whether this is an issue for you only you will know.
With that said, a few great choices IMO would be (in no particular order):
- EMI CI-880 Hybrid - Also known as the 'water drop' on some sites, it runs anywhere from $9.99 on sale to about $18 regular price. Excellent sound, decent soundstage, excellent build. They are light on the bass with the included stock tips, but using KZ Starline tips totally solves that issue.
- Einsear T2 - $10 and has a nice wide soundstage, easy to drive, and great sound for the price. Well worth $10.
- KZ ZS5 - great soundstage, great bass, and it is within your price range. Some find the treble too sharp/bright however, but you can do a few easy things to address if it is a problem for you. It sounds fine to me though. Note some people hate/bash the ZS5, but the majority of people love it (myself included). It has a removable cable, so you can swap out the stock cable for an upgraded silver plated cable, or even a Bluetooth cable option. The price of the ZS5 ranges from $12ish on sale to $20ish regular price.
- Xiaomi Piston "Fresh Version". I recently picked this up for $3.99 with a coupon code at Gearbest, and lemme tell you I was quite impressed for the measly $4 cost. However, for the best sound you'll need to lift up the mesh screens on the nozzle (using a sewing needle or thumb tack) and remove the foam plug they stuff down inside of the nozzle (then stick the mesh screens back onto the nozzle). It takes 30 seconds to modify, and can be done with literally zero skill level. Once modified, it sounds great with the genres you listed, and it's easy to drive with a cell phone as a music source. Soundstage is average, but certainly not bad. It's well constructed and comfortable to wear.
I think you'd be more than pleased with any of the ones in the above list, given your comments on sound signature, genres, budget, your overall goals, and your level of expertise.
I'm sure others will have some good suggestions as well - there's just tons and tons of great choices in ChiFi right now. Keep in mind that when it boils down to it, a lot of it is really splitting hairs between things 95% of non-audiophiles wouldn't even hear. In other words, if you walked up to 95% of the generic Joes on the street, and let them listen to any of the IEMs in the above list (as well as the dozen other IEM recommendations you're likely to get), their jaws would drop and all would say "wow that sounds really good". But ask the "enthusiastic" Head-Fiers/audiophiles and you'll get answers like "well this has more a bit more warmth in the vocals", "but that one has better instrument layering", "and this other one has slightly better extension". The choices are desire to "make the right choice" can get mind boggling, so don't get too caught up in the minuscule differences.
Another helpful, trustworthy, and honest resource is
@Vidal's site:
http://www.aproear.co.uk/review-list/
If you have any other questions, feel free to ask.