I don't think 6 watts will give you the headroom you want on 90 db efficient speakers. Even 15 watts will be, in my opinion, challenging. Although I don't know how big your room is and at what db you generally listen at.
My Zu Superflys are 101 db efficient, and most people think 6 watts is not enough, and personally I found 15 watts a bit anemic. Having said that, it can be a bit of a mixed bag here and doesn't all come down to watts. For example, while a 15 watt push pull I once had didn't have a handle on the bass, a different 8 watt 300B SET I had saw no problems at all.
I suspect this had more to do with the stoutness of the power supplies. Hard to believe that the Meng or the Musical Paradise are overbuilt in this way.
But the truth is I have no idea because I have no experience with your speakers. If you could, I'd spend more money and buy a bit more headroom. There's a user Jolida JD102CRC with a $600 asking price on Audiogon right now. It's specd at 20 watts which I think is more appropriate.
There's also a 38 wpc Onix SP3 there with a $500 asking price.