Since you are using a consumer level printer (sub $1000), the ICC profiles for the printer (you are using those, aren't you?) are probably designed to make "grandma's" photos look "better". This means that the profiles will not do well with spot colors.
A quick look shows that this printer is not on the gimp-print list (they usually have better ICC profiles), so... short of manually making your own ICC profiles (not trivial), you are out of luck.
Oh... and as much as I hate Epson software (boo.... hiss!!!), and despair the flakey-ness of the hardware, they tend to do much better on the color-matching than Canon... and usually HP (but HP is better than Canon usually).