Moving speakers from downstairs to upstairs, degrading ?

Carpet over concrete is much better than hardwood floors although the greatest benefit will come from acoustic treatments on the walls and ceiling. 

I have to agree with the majority, suspended floors sound worse than concrete slabs. 

I can speak from experience. 

Bass will sound flabby compared to slabs. 

Decoupling the speakers from the floor is your best bet.

+1 @georgehifi — I made the opposite move and went from having my system on the second floor to the basement with concrete floor.  Bass was unruly and tough to control on the second floor.  I ended up putting marble slabs under my speakers, which helped more than anything else, but you may need to put additional footers on the slab if that alone isn’t enough.  My speakers sound SO much better in the basement — totally balanced with better imaging/soundstage.  I’d keep them down there if you possibly can. 

Thank you everyone for inserting in your inputs. Greatly appreciated.
@simonmoon What are all options for Decoupling the speakers from the floor? 

it really depends.
i once had a room that was hard wood floor over concrete. that room sounded the best ive ever measured