Silverknight,
I own a music store in Southern California. I'm usually very active on the arranger discussion forum because there is more need for my expertise around there but I'm reading your post and I can offer some opinions.
currently, the price of the Yamaha Motif6 is $1495.00 and the roland RS70 is $995.00. both of these keyboards are true professtional workstations with sequencers, arpegiators and complete sound editing. The Motif also offers amazing sampling and actually sixteen 16 track sequencers so you can record different parts of your song as seperate sequences and then chain them together when you are finished.
A Rack module is the sound source within a keyboard but without the keyboard. In the Yamaha world there is a Motif keybaord and a Motif Rack. Take away the keys, the sequencer and the sampler and you have sounds only and this is the Rack!
If you like contemporary sounds such as synth pads, arpegiators I would suggest more one of the Roland, Korg or Yamaha Workstations and not an arranger. Arrangers have more instrumental sounds and fewer synth sounds and also, you can put together more layers of sounds in synths rather than arranger keybaords.
If you are in the USA and need any other assistance, please email or call me.
George Kaye
Kaye's music Scene
Reseda, California
818-881-5566