The STK4044 looks like it should do the job. The datasheet is a bit hard to read but it looks like it says that chip can handle 8ohms. I think my speakers are 8ohms so i would only be able to use 1 of them per chip.

I've just been thinking about a power supply. Am I right in thinking that ohms law still applies here? The STK4044 recommends a 51V supply. On an 8ohm speaker I work that out to be 6.375A and 325.125W. So would a 51V 8A transformer do the job? Also, I assume the 325.125W are the peak watts and the 100W specified in the datasheet is the RMS.

On the voltage, is that 51V total (25.5-0-25.5) or does it mean 51-0-51V?