i have 2 amps in my room right now and...

i have 2 400 watt MA amps ,

i have one hooked up to the converter and it works great , what if i add the second amp by usin the same power source. the power source for my room puts out 8 amps and 14 volts.

and can it blow the amps by tryin this ..?..and will it be tecnicly be puttin out 4 amps 7 volts to each amp.

If you hooked up another amp it would be in parallel with the one you have now.  Parallel wiring does not change voltage in a circuit, so you would still have 14 volts.  However, you would only have about 4 amperes to each amplifier cause a parallel circuit divides the current.  That is assuming that each amplifier is identical, and you said they were both 400 watt MA audio amps. 

I did some quick math and found that you can only get about 112 watts total power into the amp you have hooked up now with 14 volts and 8 amperes only(volts times amps = watts), and the amp won't be 100% efficient anyway so you would only get about 55 - 70 watts back out of it based on an efficiency factor of 50 - 60% and that is assuming that it is a class A/B amp and not a class D.  Class D's can be as much as 90% efficient so I'm told, but that would still only be about 100 watts total.    These are rough figures but they are no where near what it's rated at.  If you put another amp on the power supply, then you won't even get that from the one you have hooked up now.  And the power supply would run pretty hot trying to supply all the current your amps would try to draw from it.  Take an example from VWBobby's amp and power supply.  His is a 60 amp supply to a 500 watt amp.  At 14 volts, it can supply 840 watts of power to his amp.  If his amp is at least 60% efficient, then he can get the whole 500 watts from his amp.  His power supply would have to run at maximum though to get it, and his is way bigger than yours.

I say do not do this.  You need a larger power supply just for the one you have to get it's wattage rating up anyway.  I don't believe it would hurt the amps any, but the power supply would probably not last. 

Yeh your converter is to small but also if you connect 2 amps to the same power source you share that ampage but as long as you source has enough output power the voltage to but would be 14v.

Also an amp will only take as much power as it needs eg. if you have a 100A  14v PSU and connect an amp that only needs 10A this would be fine the PSU would keep the other 90A in resurve for any over items you connected.