Hi guys, It's my first post here. I've been reading around for quite some time. OK let's get to the point.I just bought the Oppo PM-3 and it's fantastic. However, I found that it lacks impact and deep bass. It lacks some fun. The kick drum and bass groove just aren't there. Can you guys recommend me any portable DAC/amp to help with this issue? I've heard of HA-2 from Oppo, the same brand, with bass booster and got interested in it. But I have no idea of other DAC/amp models out there.Please recommend me some. I'll use the DAC/amp with iPhone 6 & Oppo PM-3 headphone.The DAC/amp needs to be portable, and I don't wanna spend more than $300. Thanks a LOT, guys !!Duke