Okay, there is another issue that you did not ask about. It is better to get subwoofers that are all identical to each other, and it is better to get really good ones. A whole bunch of cheap subwoofers do not add up to equal performance with a good one or two. I recommend that you save up your money until you have $500 or more and buy an SVS subwoofer. Here is what I would buy for $500:
SVS PB-1000 - 300 Watt DSP Controlled, 10" Ported Subwoofer
That is a great subwoofer for that price. If you then want to upgrade, buy a second one.
As for your specific questions, you would use a Y or more than one Y connectors to split the subwoofer output signal (from your Pioneer receiver) to enable you to hook it up to all of your amplifiers used for powering subwoofers. With the idea of two passive and two powered subwoofers, you need to divide it into 4, so you would go from a Y to 2 other Y connectors, so that each of these goes to the amplifier driving each of the subwoofers. In the case of the Mirage and Velodyne [do you mean a CHT-8R or something else?], the amplifier is built in, so you plug one end of your Y to each of them, and in the case of the unpowered subwoofers, you are using the Technics receiver, so you would plug your other Y into a line level input (like the CD input, for example), and hook up the unpowered subwoofers to the main right and left channel speaker connections in the Technics. You would want to make sure all surround processing of the signal was off in the Technics. And you need to select on it the input to which you have hooked up the subwoofer line connection (e.g., CD if you plugged into the CD input). The volume control on the Technics would function like the level control in your powered subwoofers.
If you used 1 unpowered subwoofer, you would plug into one channel of the Technics, either the right or left, and then hook up the unpowered subwoofer to that main speaker channel output (either right or left; whichever channel you selected for inputting the signal). And in this case, you would only be needing 2 Y connectors for the line level subwoofer signal, as you are only dividing the signal into 3 instead of 4.
Again, I do not recommend that you run these different subwoofers together, and that instead you sell off the ones you have (if you can get a tolerable amount for them) and put your money into a really good subwoofer from SVS. I strongly recommend that you do not buy any more cheap subwoofers.
