Some close up lenses work better on a particular camera than others. As Danny (a very accomplished macro shooter) suggests, one of the problems is the glass in front of the lens. It may take a bit of experimenting (or less costly research), to find which lenses will work for you.
The images you posted exhibit a fair amount of distortion and softness. Some of this may be caused by camera shake/motion blur (more on this later), some from ISO noise, and some from cropping. But some is certainly attributable to glass quality.
If you're stacking all 3 lenses (the strongest lens should go on first), then you have a total of 9 diopters. Switching to a high quality Nikon 6T will only net you 3 diopters. A Canon 250D only brings you up to 4 diopters. Stacking a pair of 250D's will net 8 diopters (at a cost of $175 or so), but will give you the magnification closest to what you currently have. I like to stack my 6T on my 250D for 7 diopters (it's a very versatile combination). And fortunately, stacking either of these lenses will still produce a high quality image (low distortion, high sharpness, contrast, and color fidelity).
If you're set on extreme macro (what I consider to be above 8 diopters), then another option would be to mount a lens Reversed on your camera. Usually a 45 - 55mm "normal" lens intended for a 35mm SLR is used (yielding a diopter value of about 15). They can usually be found used for well under $100 (get an f1.4 to minimize vignetting). In addition, I like to use a big "Enlarger" lens for a lot of my macro (about 7 diopters equiv).
Let me know if you want more info on those.
Now to address the possibility of camera shake/motion blur. 1/125 sec is Veeeeery slow for these magnifications. You need a LOT of light to shoot macro in available light. You're in a bit of a quandary, because if you up the ISO, noise will become very prominent. If you open up the shutter, you'll lose DOF. I'd suggest using flash until you get more comfortable handholding in available light. Flash has the advantage of all but eliminating camera shake and motion blur (leaving you to concentrate on focusing - a great challenge in itself).
I like using off-camera flash, but a flash mounted on-camera or on a bracket will work very well. Here's a pic of my setup (717, reversed 135mm f4.5 enlarging lens, makeshift hood, and a Sunpak 383 with a homemade softbox). Flashlight velcro'd to the lens barrel for focusing in low light (I love to shoot macro at night):
Try doing some testing using flash to see how sharp your lens(es) are (without camera shake/ subject blur as factors). Or use a spotlight so that you can get the shutter speed up to 1/1000 or faster @ f8.
One thing to note: the image quality problems here aren't due to narrow DOF (although narrow DOF is a factor that you'll have to deal with). Your V1 should produce some fine macro pics, and you yourself are obviously very capable!
R2
ps. Below is a pic taken last summer with my 717 and a single 250D (images is cropped a bit).
--
Good judgment comes from experience.
Experience comes from bad judgment.
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) and at 4x optical with just +3 or +4 by themselves should be ok for most people. Also.......and I better say IMHO, try digital zoom as well. The reason being that from what it looks like here, it will be better than stacking anyway. Some cameras and especially from Sony I've noticed, the digital zoom algorithms are better than cropping with software........better say IMHO again 
