I assume you are talking about a surround sound system, they have the cheap ones at Walmart for about 100 dollars. They just get more expensive from there though.
Antenna amplifiers are used to strengthen the signal being supplied to an appliance such as your TV. Amplifiers are necessary when the signal is weak and interferes with your TV reception.
Yes most of the new home theater systems come with integrated amplifiers
Many Yamaha amplifiers can cost you around $499 or higher.
Convergence amplifiers.
There are many companies and websites that offer television signal amplifiers for sale. Some of these companies that offer amplifiers are NewEgg, Walmart and Amazon.
A quick search of this incredible question brought fourth some greater insight into the matter. It turns out the applications valve amplifiers are used for vary from guitar amplifiers, satellite transponders, audiophile stereo amplifiers, military applications and high power radio and UHF television transmitters.
Kicker amplifiers can be a bit expensive, especially compared to other brands. They can run anywhere from a couple hundred dollars up to a couple thousand depending on the wattage, but you are paying for quality.
NBCUniversal Television Distribution was created in 2004.
CBS Television Distribution was created in 2006.
American Television Distribution was created in 2004.
There are two ways to route television signals to several televisions. The first is to use an RF distribution amplifier. These take a feed from an antenna and route it to several outputs. RF co-ax cable is needed to run from the amplifier to each of the televisions. Every television can receive any of the channels available through the antenna. The other method is to use a receiver such as a digital set top box, a cable or satellite receiver and take the output into a video and audio distribution amplifier. This works well for standard definition video but HDMI distribution amplifiers tend to be expensive and not all televisions will work with all amplifiers. This is due largely to the content protection systems employed in HDMI signals. HDMI of course is the only method of running HD signals in a domestic set up. Note that each television will only display the program that the receiver is sending out so there is not facility for multiple programs from the single source. Cabling for standard definition will be a video co-ax and a pair of audio cables. The co-ax should be a 75 ohm type such as RG59, URM70 or similar. RG59 tends to be the least expensive and for runs below 50 feet or so, is perfectly adequate. HDMI cabling must be bought a a complete cable assembly and prices rocket as the lengths increase. It's worth thinking carefully about what you want to distribute and how you go about it before investing in cable or hardware.
A distribution amplifier can be purchased on-line from the manufacturer or other website stores that stock this product. Distribution amplifiers can also be purchased at large electronic retail stores.