rca splitters

This setup is actually in my boat. HU is a Sony CDX-GT610UI a few years old. It only has 2 preamp outputs 1 pair labeled L and R. Each one has a splitter and they all go to a 4 channel amp, which runs 4 speakers and one sub. I want to add an another amp and 2 more speakers. The big question is .....How many splitters can I piggy back onto each other in order to split and have enough RCA's to got to both amps.

As many as you want.

As long as you are willing to deal with issues associated with low voltage at the pre-amp level. Increased noise floor, increased potential for alternator whine, possibility of decreased performance from the amplifier. If your head unit clips before the input stage of your amplifier maximizes its potential, you have a performance loss due to your y adapters. This is dependant on the amplifier design. Better amplifiers will suffer the most while cheaper amplifiers tend to have an input stage that over gains the amp and sacrifices the noise floor. You might be able to add the y adapters that you need and never encounter any issues, but be aware that there are limitations. If and when you run into problems you will know why.    I suggest trying the adapters and if you are a true enthusiast, upgrading your head unit and or adding a high voltage preamp like the ones offered by Audiocontrol.

The input impedance of any modern day amplifier is at LEAST 10,000 Ohms, 10 amplifiers all connected to 1 set of RCA cables will result in a 1,000 Ohm load on the preamp output of your radio.  Any modern day radio will put out just as much voltage into a 1,000 ohm load as it will into a 10,000 Ohm load. 

Well then it doesn't look like this is the best way to go. What are my other options when it comes to wanting to add the 2nd amp and 2 more speakers?

Wow.

man you guys are a tough crowd. I misunderstood the whole OHM's analogy with all the ZERO's in it. I'm a fireman, and that stuff in no it my dictionary of lingo. However, I would like to follow up with a another question. Can I leave my EXISTING setup the way it currently is and then ADD an LOC to the speaker level outputs on the back of the HU? that would be a 2 channel LOC just to the NEW amp with 2 NEW speakers. So then my current setup runs from the 2 RCA's and the NEWLY ADDED setup runs from the speaker level outputs. Pretty much 2 independent systems. Does that make sense and is that another option?

If you want to be able to fade front to rear, then yes you will need to use the LOC connected to the front speaker outputs of your radio. 

If you do not need to control volume separately, splitters are your best option.