Shure Vocal Masters for center channel :P

I've used those, and they're awful. They'll make loud noise, but you won't like it. They were actually part of a set that included a 6 channel tube-powered mixer. I still have the old mixer.

Good PA gear doesn't sound worse than good home audio stuff or have the high frequencies rolled off, although it tends to be designed with different goals. (i.e. you might not want a pair of KF850's in you're living room as they'll lose coherency inside of 15 feet or so, but in the right space they're great speakers) These were cheapo even when they were new, although that type of "column" speaker had some popularity for a while for venues looking for PA systems that were cheap and loud but didn't need to sound great for music reproduction. (churches, high schools, garage bands) Peavey had some speakers that were very similar with 4 12" woofers and a compression driver. Even today you'll find big cheap speakers designed for a similar crowd. The speakers I linked sound like crap too. Now it's possible that if you need to fill a large space with dialog only (i.e. you need louder rather than better) then maybe such a speaker could yield satisfactory results, but I kind of doubt those particular speakers could accomplish even that. Sorry to be a downer...

My gawd, no. Just... no.

It will make your HT sound like the high school PA from 1960.

Yeah, they're crap, but I guess that should be expected from something so cheap. That is comically small for a 15" woofer though. The EAW's I referenced above have a larger voice coil on the compression driver. (which is 112db efficient and rated for sustained output levels of 135db and peaks of 141db )