I shipped a 2x12 Marshall to Cebu years ago via Air21. I boxed it OCD style (hehe) and Air21 picked it up at my house. The people who picked it up gave an estimation of how much it would cost which they said will have to be confirmed at their offices. I paid their estimate and received a call by the company the next day, saying that my payment was over a hundred pesos over. I let it go and asked them to proceed with the delivery. Amp arrived at my buyer's Cebu address 3 days after it was picked up at my house. It cost me about PHP2K then, IIRC.
About a month ago, I bought a small tube amp from a PhilMu member. It was sent to me via LBC and I received it the day after it was shipped. I believe LBC has that pick service as well.
You could also opt to send it via PAL or Cebu Pac cargo. This method is a lot cheaper. Only problem is, you would have to bring it to their cargo offices while the buyer gets it at their local PAL/Cebu Pac terminal. The item usually arrives within 24 hours (or same day even, if you bring it early and there are lots of flights out to the desired province) as well, depending on flight load. PAL's cargo office is near Terminal 2 while Cebu Pac's used to be at Terminal 4.