[danpen]

SRGB is designed to display reasonably well on non colour managed systems, it has a relatively small gamut but is good for web images where you can expect the majority of your audience are not using colour manged applications or calibrated moitors. Therefore images for the web should be converted to SRGB (as the Save For Web and Devices function in PS does).

You perhaps won't see a substantial difference using other colour spaces but personally, on the odd occasion I do any real editing on an image, I prefer to work in 16-bit and use something with a larger gamut such as Prophoto RGB to preserve the colour detail and then convert at the last minute.

Non of that's likely to help, the important thing is to ensure that

1. The heads are clean and you've no misfiring heads - there should be a utility with the printer to check that.

2. You're using a colour profile suitable to the ink and paper you're using (is this problem with manufacturer inks and paper or 3rd party?)

3. You're only doing colour correction in the software of the printer driver - not both.

cheers

Dan