... a 3rd monitor is less than half the cost of the HT center. It looks great, but hard to justify.
A common misconception is the center speaker is an "add-on" because it is only for dialog. Most of the time the L&R speakers will only have ambient low level sounds and music unless you have a steady diet of blockbuster action movies. All the sound is coming from the center speaker. Because of this, the center is usually a lot louder than any other speaker in a home theater. Dialog is tricky, one reason dialog is hard to understand besides lousy mixing in most movies is low quality center speakers.
Once in a while I forget to turn on the L&R speaker amp, I have four different multi-channel amps for my 7.1.4 theater, it's easy to screw up sometimes. When I turn everything off at the end of movie night I realize the L&R speakers were never on and I didn't miss them.
I have three Dennis Murphy designed front speakers, the Salk HT2-TL and the HT2C which uses the exact same drivers. The difference is the center speaker is smaller with no port. A port muddies up dialog. A center speaker should just have clean, clear direct sound, any extra sound like from a port will add a little out of phase sound from reflections plus male voices get a little chesty, good for music but not for speech. Many movie fans complained that they couldn't hear or understand the whispers in Dune 1. I had three Dune viewing parties and none of my guests complained or ask "what did they say?"
Home theater processors filter out low frequencies around 80Hz to all speakers, the 55Hz frequency response of the Philharmonic HT Center Channel is perfect.
Long after you forget about the added expense you and your family will still be enjoying the flawless sound. And nobody will be asking "What did they say?"