Squeak,
I'm glad you spent the time with the 3k and found it wasn't for you.
We all hear with different ears,and we all use our boards for different purposes.
I played the RS-70 and found it totally useless for what I do,which is playing "live" with a style backing.
It probably serves some purpose,but it is not on my list of keyboards to own.
Thankfully the 3k is perfect for my needs,and, as I have already said,it is by far the best arranger for the money,and better than some other brands that cost a lot more.
Again,sound is subjective,but after playing the RS-70,I feel that it's sounds are no where near as rich and powerful as the 3k.Of course,that is my opinion.
The RS-70 is an entry level synth and as such,it falls short of the other offerings by Roland both in key feel(the one I played had already developed noisy keys) and polyphony.Also not having aftertouch was a serious omission.The D-Beam was fun.
Perhaps the Juno G will be what you seek.
The MO 8 is a nice board...I played one this past weekend.Lovely action...all smooth and brimming with quality.

All the best, and may you find the right keyboard for your needs.
Ian