Hello, everyone.
I just wanted to let you know (if someone is interested) that I decided to go with "Transcend PDU3". I purchased the card, installed it and for now, it seems to me that it works fine . Currently I only have one USB 3.0 memory stick (32 GB AData S102), and managed to copy approx. 15 GB of data from it with an average speed of 63.5 MB/s. While it's not so much (actually, it's just a little above upper speed limit of USB 2.0), it is more than 2x faster od that same memory stick when connected to USB 2,0 port, so I'm happy for now. In a few days I'll have one external USB 3.0 HDD and will see how it works.
All in all: if anyone is in same dilemma I was 2-3 days ago - it seems that Transcend PDU 3 works just fine under Linux.