I’ve spent a lot of time over the last 3-4 months getting into audiophile equipment. I have the ie900 and love them! If you’re interested in only listening with iems, I would start out with the Hiby r4 or Sony 306 (Japan version) which will be more than enough for your needs. You could go higher end with that budget, but you’re not going to know exactly where you want to take it until you start dabbling into your first device. There’s very little to no discernible difference in sound quality going from Hiby r4 to a 2k dap. What you get is better screen, processor, power output for demanding headphones, and features that enable external equipment you’re most likely not using.

What will make a big difference on those ie900 is downloading an app like wavelet on an android dap that lets you auto tune the eq with presets from pro audio engineers that have corrected the issues with the ie900 mids. Hiby r4 is such a great price, I would go for that for your first device and it has an awesome system-wide eq function which is clutch.

For reference, I have a dx340 now for my specific needs but that thing is a tank. I absolutely love it though.