Digital BW, The Print

Hello All.

Perhaps this has been covered; I have tried searching the archives,
but am not really sure what to search for.  If so, I apologize.

With the 8 ink carts on the Epson 4000, I have been wondering if it
would be possible to load one up with 2 ink sets, one quad-tone for
b&w printing, and one color for, um, color work.  My main priority is
top quality black & white printing, but if I am going to spend the
money on  a state of the art technology like the 4000, I would not
mind being able to  produce the occasional color print as well.

First, is this possible? If I understand properly, some of you are
using  multiple quad sets for variable toning effects, is this any
differnet than that?  Would the color output from 4 inks be noticeably
inferior than that from the newer 6 or 7 ink sets?

Second, if it is possible, what does it take to do it?  Is there a
preferable RIP for this type of thing (I am heavily commited to the
Mac)?  Any additional tools required to profile/linearize the thing? 

Or... should I just dedicate a re-furbed 7500 to b&w, and send the
occasional color print to the service beureau?

Thanks for any input.

Chris