Hello Spalding
To my ears they seem to lack the true sound of a piano. (Too hollow)
Another option to consider is the use of Akai samples (The largest studio quality sample library on the planet) as according to the PA1x brochure they can be loaded in. (Just be careful of sample size as some of the better ones can be up to 128Mb in size, and there may be larger ones)
Do a Google search for Akai Piano Samples (Many have demos) and see what�s available, that are suitable for your PA1x.
Hope this helps

Bill