soft proof vs preview before printing

Hi to you all,

I have been struggling to get a good printout of my photos but this is really very hard to achieve.
Pls tell me what is it that I do wrong.

I am using cs5.
my printer is canon pixma mg 6250

here is the way I follow:

1) I am using redriver paper.com's printer papers.(to do that I have downloaded the icc printer profiles for my pixma mg6220 and then installed these profiles.)

2) before going to the printer dialog in cs5, I first soft proof my image to see if there's a gamut warning or not.

and to do that I select the paper I will use under "device to stimulate" and chose "relative colorimetric" and "black point compensation"..As soon as I see that there's no gamut warning I go to the printer dialog.
3)in the printer dialog I choose:
a)photoshop manages colors.
b)I disable printer's color management.

c) printer profile setting: I choose the paper I want it to be printed. (ex: redriver ultraprosatin for canon)
d) I chose "relative colorimetric" and "black point compensation"

e) I set the Media Setting: Photo Paper Plus Semi-gloss and Quality to Level 2 (these are the recommendations from redreiverpaper.com for ultra pro satin paper typr that I use.

f) check the "preview before printing" option

4) and finally I press the print button.

before the printing starts, I see the preview of the image and this is where I have problems.

a)on this preview, the colors of the image are totally different than the original file (when I first open the file from the file menu)

b) this preview colors are also different than the soft proofed colors. (I will send the printscreen image in a couple of hours and there you can see the color difference between the preview form and the soft proofed form)
I cant understand the reason.
shouldnt this preview colors totally match the soft proof colors?
(if not why do we soft proof.)

and in my experience, when I finish printing the image , I see that the colors on the paper are very close to the "preview" colors but not to the colors of the soft proof.

I can't find out what I am doing wrong and in the while I spend lots of paper and ink.
So pls tell me what my mistake is.

one more thing to add:
my monitor is samsung sync master and I can not say it is calibrated but

1) I have done some basic monitor calibration with the help of a samsung calibration software which came with the monitor..so I can say that a basic calibration exists on my monitgor but not a professional one.

2) when I take my photos to a lab, they print them wihout any color adjustments and they are perfect, exactly the way I see them when I open at cs5.

so which is the exact match of the final output, the preview before printing view or soft proofed view?

thank you in advance
Melih