My grid is screwed in GECK...

When I duplicate anything, it never fits with the other parts in my area. How come? Pretty annoying I have to adjust everything.

file:preferences: snap to grid and snap to angle, these should be powers of 2, the lower the better
powers of 2: 2 4 8 16 32 64 128 256 512 1024 2048 4096
didn't use a calculater, that was straight memorization

I use 4 or 8, depending on what I am placing.

Part of the problem may be the objects you're duplicating. If you duplicate an entire cell (including furniture and clutter), you'll run into the problem you describe because furniture and clutter aren't aligned to the grid. If you load a vanilla cell (one from the un-modded game) and double-click on a piece of clutter (like a book) in the Render Window, you'll see that the X,Y,Z coordinate aren't powers of 2. The same goes with furniture. For instance, I double-clicked on a couch in AlexandriaArms01 and found the following coordinates for it:

X: 4303.2637Y: 1993.1892Z: 7010.6763

Clearly not divisible by powers of 2. When I double click on the floor underneath the couch, I get the following coordinates:

X: 4320.0000Y: 1968.0000Z: 6976.0000

Clearly all divisible by 2, 4, 8 & 16.

Now, if I try to duplicate that cell and align it to something, it won't align properly because the couch (and anything else with coordinates not evenly divisible by my snap grid setting) will throw the system off.

Bottom line: If you absolutely have to duplicate a cell, don't try to align it with anything until you eliminate the clutter, furniture and anything else not perfectly aligned to the grid. In fact, it will most likely be quicker to just use the available tilesets to build you're layout piece by piece.