I could be completely wrong about this (see my post above)
I think, whatever colourspace you work in, you need to ensure that as it saves for printing, it is /converted/ to sRGB (if that is the profile that the end process is expecting).
If a profile is just 'assigned' to an image, then all it does is effectively call one colour the other colour.
Have you used the curves tool at all? The way that images are saved is that they record a number for a particular value of Red Green or Blue (or Cyan Magenta etc.etc.) for every pixel position.
In order to display this information as an image, they send the values of Red Green Blue to the monitor.
As the information passes through the system, it effectively goes through a 'curves' translation. I.e., for each RGB value, they are looked up on the horizontal axis, and a new value is read from the Y axis. This is to allow for any changes that there may be one from piece of hardware to the next. I.e., if a monitor is dark compared to another, then its 'curve' may be steeper than the other's.
This is all OK if the curves are just linear responses, but if they are non-linear, then converting back from one curve to another is not always easy/possible.
So, if you sent off a print to someone, with a huey profile assigned, and they didn't have the correct profile, if they try and convert back without knowing the exact curve, then their 'best guess' might not be what you intended. However, if you convert to RGB first, then this should be as they expect, and the conversion is done on your computer, where your computer knows how the conversion was done in the first place.
As a test, (I think you had photoshop?)
Load an image, and go to edit->convert to profile. Select Adobe RGB 1998 (don't press enter, leave it selected, so long as preview is selected, that is enough).
Press the down arrow a couple of times (at least 5, pre-photo is a good example here), and that will preview the changes to you. You will see some slight changes, but not much.
Now, click cancel, and choose assign profile. Photoshop might warn you, this is what we want to see. Select Adobe RGB again, has it changed much? Press down a couple of times, till you get to pre-photo. Probably looks awful now.
If you send an image to a print-shop, with a profile on the image, which they do not have, all they can do is assign one which 'looks good'. That is if they even use humans, if they don't use humans, then they will just assign one at random.
