There are a few different ways that you can hook up 2 amps to RCAs. The most common way is to use a Y-splitter, which will split the signal into two separate signals, each of which can be amplified by its own amp. Another way is to use a dual-channel amplifier, which has two channels that can each amplify a separate signal. Whichever method you choose, make sure that the amplifiers are properly matched so that they don't overload each other.