To answer your subject question, you'll need to provide more information. Specifically, what are you using the computer for, and what are the timing and voltages of all four sticks?
In general, you shouldn't mix RAM of any type, not even if of "the big 3" (Frequency, Timing, & Voltage), only one value doesn't match. The typical results of RAM mixture include, but not limited to: Blue Screen of Death (aka Stop Error), instability (freezing/crashing), unusable RAM.
The problem is that the BIOS can only be configured to one set of specs at a time, regardless if you use the [Auto] (default) setting or manually configured. For that same token, it is often best to manually set your DRAM values, in the BIOS, to match the specs shown on the RAM (on the stickers). When you have a mixed set of RAM, you can run into problems because of the physical limitations of the RAM.
For the sake of simplicity, let's say your RAM (from your list above) has these specs:
Remember, these are just assumptions, as I do not know what your RAM specs actually are, except for the Frequency. As you can see, if these were your actual specs, the lingering question is "If you were to install all four sticks, what would you configure your BIOS to?"
Realistically, you can't. In this example what you'd have to do is set the DRAM voltage to accomodate for the highest of the set, which is 2.1 V. Next, you'd have to set the timing to accomodate the loosest of the set, this would be 7-7-7-24. Finally, the frequency would have be set at 667 MHz, despite two of the four capable of reaching up to 800 MHz.
The problem with doing what was mentioned above is that this configuration is so convoluted that one or more of the RAM sticks may not be flexible enough. For example, maybe stick one is too sensitive and actually starts to burn because it can't handle 2.1 volts. Or maybe stick four needs to be operating at 800 MHz to use that loose of timings. The biggest difficulty is that with the configuration so diverse, there is no way for you to test, accurately, which stick has what problem at which of the manually specified values.
On the other hand, you could also be very lucky in that you'll see no problems by leaving the DRAM settings on [Auto].