Here's how to determine the impedance of the speaker. https://www.wikihow.com/Measure-Speaker-Impedance
It's harder to know how powerful a stereo amp you need to run them. The power ratings of HTS systems is usually wildly exaggerated so finding the specs of the original amp can be a waste of time. The speakers may not sound good because they are meant to be used with a subwoofer which you don't have.
Unknown. You need to know what the impedance of the speakers are. Many home theater "kits" like this have low impedance speakers that are not suitable for other uses.
Don't get sucked in by "home theater." To audiophiles that's a dead giveaway for Walmart Speakers. But short answer u probably need an amplifier capable of driving 4 ohms. Now it maybe cheaper just to buy 2 self-powered speakers, depending on what u gonna be using for.
Here's how to determine the impedance of the speaker. https://www.wikihow.com/Measure-Speaker-Impedance
It's harder to know how powerful a stereo amp you need to run them. The power ratings of HTS systems is usually wildly exaggerated so finding the specs of the original amp can be a waste of time. The speakers may not sound good because they are meant to be used with a subwoofer which you don't have.