Fast prime for indoors. Suggestions please.

Of course it's not very fast, but it's versatile and the extra couple of stops do help a little. Comparing it to the 50mm 1.8 the OP mentioned it does quite well since the 50 has to be stopped down anyway. A 1.4 lens is faster, assuming you can use it wide open, but it's just another couple of stops. We are always just chasing those 'couple of stops' tho, aren't we

And I tend to run into the DOF issue anyway, so 2.8 is already problematic for anything other than a portrait