I'm looking into getting a VP180, as long as my Yamaha RX-V659 can drive it (it has a 4ohm setting for L/R inputs so I'm hoping?)

Question is what to do with my current VP150. I just installed a plasma in my bedroom and the internal speakers obviously are lacking. Thinking of mounting the VP150 below it, connect an amp and run a downmix to it? Kinda like a poor man’s Polk/Yamaha DSP speaker?

Would this work?

Sure. I don't see why not on the question of a VP150 as a mono TV speaker. Normally, anything is better than the internal TV set speakers.

However, don't use the 4 ohm setting for the 80s. For electronic reasons better explained in other posts, you should never use the 4 ohm switch provided on some receivers. Your Yammy will likely have no problem driving the efficient 80s at 'safely loud' volumes or even a bit beyond. The 4 ohm setting can cause more harm than good.

Nach, this has been discussed here quite a few times, but as Andrew indicated, the 4 ohm setting shouldn't be used. It in no way optimizes performance, instead it simply reduces the voltage output of the power supply section to lower the chance of overheating and satisfy UL(Underwriters Laboratory)requirements. Following Ohm's Law, when the voltage is reduced, so is the current and power(and thus also the chance of overheating).

When lab tests have been done(e.g., S&V)use of the lower setting has cut maximum power roughly in half. So, overheating risk is reduced at a cost to maximum performance capability, and the setting should be left at the higher default.