There are a number of RGB amp threads here, some for op-amps and some for transistors. In them, the various pros and cons are discussed, including the op-amp type and impedance issues. (I'm too lazy to find them now, but they ARE here). I remember specifically that I was the one who guessed what op-amp was actually being used before that info was even published.
$25 is not too much to spend for a pre-fabricated PCB, especially if you consider that the PCB kit is probably a high-volume (= low cost per board) item; the Expansion Interface board I show here, given that it is low-volume (can't get much lower than one!), cost about $150, plus my time in design and component install. But given, as I said, that both the op-amp circuit and the transistor circuit are available here, just use one of the prototype houses that will make the PCB for $9.99, buy the parts, and build it!
So, anyone want to do some research and determine what size PCB you actually could install in whatever unit, preferably in all three dimensions? Then let's see what circuitry will fit on it. (Hmm, don't forget you need cable connectors some place!)
Charlie