I currently own the Cayin A-88T/6550 and owned the ASL AQ1001DT in the past. I enjoyed the sound quality of the ASL, but the build quality is a definite step back from the Cayin. In a side-by side comparison, I don't think anyone would dispute this. Everything from the remote to the the output transformers to the chassis itself is more substantial on the Cayin.
In addition, I agree with the owner of VPI that the Cayin A-88T sounds better than many more expensive separates. I am reluctant to compare the 2 amps sonically because I've used different components with each, but I will state that the Cayin sounds really, really good.
I was told by Acoustic Sounds that the 6550 output tubes add a little more resolution and frequency extension compared to the KT88 tubes -perhaps this is because the 6550 tubes in the Cayin are the more premium ElectroHarmonix tubes and not generic output tubes as used in the KT88 version.