You wouldn't have to rely on the monitor's cheap built-in speakers if it had audio output (like 3.5mm stereo or a "headphone" output port). You would lose 5.1 surround sound but you were going to lose that anyway. Then you can plug in pretty much any set of speakers through the monitor's headphone output. At this rate though, you will likely be able to find a 1080p LCD HDTV at a lower cost than a 1080p monitor. You also know that an HDTV will have speakers built-in. I purchased a 27" 1080p Vizeo LCD HDTV ($200) earlier this year that was $50 less than my 23" 1080p HP monitor ($250). My monitor was an IPS LCD display but still, you get the idea.
The other thing about the monitor is that it needs to be HDCP compatible. That was an issue a while ago but most monitors, especially ones with HDMI input, tend to be HDCP compliant.