You have the ed9 and edr1 from the ultra budget segment. I think they're the greatest in the ultra budget lineup. If you wanna know more, you can visit TheContraptionist (@B9Scrambler's website) as he has a dedicated post in which he has described every KZ he owns (and he's got even a few KZ which aren't actually easy to find around that can be a great choice if you wanna expand your collection). If you don't search for KZ, then at like 15$ you could try the UIISII CM5 and obviously my beloved EZ AUDIO D4. I've written a little super easy MOD some time ago. Buy a pair of EZ AUDIO D4 and put on a pair of starline tips pushing them very hard until the nozzle ends, you'll hear which kind of bass you can carry out of them. I think one of the most powerful bass responses i've got in a micro-driver for under than 10 euros.